Messy Interactions

Being a lazy pony was something to which Rarity would never admit. First of all, it was not true, and second of all what she was doing this afternoon was not, strictly speaking, being lazy. In her line of work she could never afford to be lazy. Lazy had not allowed her to expand her fashion empire into Equestria’s capitol city and now into the Chrystal Empire. And lazy had not gotten her the bits necessary to purchase this penthouse apartment both overlooking the Celestial Valley and within easy walking distance of the gates of Canterlot Castle itself. To be honest, what she made selling dresses to Canterlot nobility had not been enough on its own to afford a place such as this, but with what she made at her other “career”-so to speak- it had been sufficient. That's not to say she no longer considered Ponyville as her home, quite to the contrary, this penthouse was simply where she came to stay when business matters kept her in the big city for more than a day at a time. Her connections to that town ran far too deep for her to ever consider abandoning it no matter where her business interests took her.

Besides, in terms of stress relief what she was doing now wasn’t so different from thoes wonderful spa treatments she tended to indulge in while living in Ponyville. Despite feeling a twinge of guilt at the vanity of it all Rarity couldn’t help but yet again stare at her reflection in the huge custom mirror taking up half the east wall of the sitting room. A room larger than most full bedrooms located off to the side of the penthouse’s master bedroom. The image staring back at her was one of a beautiful young adult mare with perfectly styled mane laying on her side on a plush red velvet sofa, eyes half closed in strange combination of sleepy desire. Had any other pony been lucky enough to see the same image as Rarity was now enjoying they would have immediately taken note that the mare in question was encased in a very tight, form-fitting black pvc catsuit.

Well, perhaps strictly speaking it wasn’t a true catsuit, it didn't cover any part of her head, nor did it cover her hooves, but it was close enough that she wasn’t about to bother with semantics. Many years ago when she had begun to experiment with wearing such garments she had bought a similar looking catsuit made out of latex. In the end the difficulty of maintenance, keeping it out of direct sunlight, having to use a special oil to keep it as shiny as possible, keeping it from being in contact with metallic objects, etc., etc., had keep Rarity from wanting to ever own anything like it again. Despite this dissatisfaction her desire for tight shiny things never truly went away and when pvc plastic began to be used as a clothing material she had jumped at the chance to try it out. The first ones she had tried were cheap and tore easily, but the artificial plastic material held so much more promise than the naturally occurring latex when it came to durability and ease of care. Undaunted, she had purchased more expensive versions made from thicker plastic and she had even begun to experiment with making her own. The process was not straightforward and required the purchase of new machinery for her design space but decent results were eventually had, much to her glee.

And now years later she was able to lay down and relax in a perfectly formed pvc outfit of her own design, made by her hoof picked employees. Rarity adored how its slick shiny surface reflected the light streaming through the large bay windows of the sitting room in fascinatingly different ways with only the slightest movement. She loved how it looked stretched tight over her firm thighs and toned legs. And she never got tired of how the slick interior of the catsuit felt as it slid over and pressed down on the soft fur of her entire body.

Under regular circumstances she would have found the catsuit alone to be enough for a good night of fun, and as a way of substantially increasing her monthly income. Not many mares who saw Rarity wear the thing at parties could resist paying a substantial sum to be the filly lucky enough to go home with her for the night and be licked and fucked in places they didn't even know had existed by one of the sexiest mares in Canterlot. However, this was not a day for parties- yet, which suited Rarity just fine, as the catsuit was not the only thing she was currently wearing. Any halfway observant pony would have noticed -after getting over the initial shock of seeing a pony as naturally good looking as Rarity wearing such a thing- how the catsuit bulged out around Rarity’s butt and crotch in a way not quite natural. One of the best things about a tight pvc catsuit not normally recognized even among the mares who commonly wore such things, was that if one were to wear a diaper underneath, the catsuit would hold that diaper very tight against the body of the mare in question. And of even greater importance, especially to a mare such as Rarity who is a bit obsessive about maintaining clean living spaces and personal appearance, the tight shiny plastic makes a perfectly moisture proof barrier between the diaper, -should the mare wearing it choose to use it for its intended purpose- and anything she may want to lay or sit on. Rarity loved being able to relieve herself of the concern that she might inadvertently stain anything she may try to sit on in her luxurious apartment simply by pulling one sexy garment over another.

All this was at the moment quite helpful, because Rarity was indeed currently wearing a very well used diaper under her catsuit, and without it she wouldn’t have dared lay around on one of her favorite sofas. Again she groaned as she turned herself over onto her back feeling the slimy mess in her extra dirty diaper squish between her exited pussy lips as it was pressed down into her crotch by the tight pvc surrounding the diaper. Every movement made her take a moment to steady her breathing and close her eyes as the new wave of pleasure passed over her. The true fact of the matter though, was that as amazing of a feeling as simply being in a diaper this wet and messy under a pvc catsuit was, it was only the second most dirty and erotic thing about her current situation.

The thing that really kept Rarity’s pulse racing and clit leaking was that the diaper she was wearing and the mess it contained were in fact not her own. Both had belonged, only an hour before, to the single hottest mare Rarity knew of. Her gorgeous, adoring, intelligent, cute, and sexy as fuck, little sister. Just thinking about Sweetie Belle’s warm slick brown shit- yes, shit, it felt even hotter in her mind saying it that way, coating her butt and being pressed into her pussy and up her vaginal canal with every rub to her crotch, was nearly enough to make her cum on the spot. Only years of practice at restraining herself in countless sessions of hot sex with thousands of mares kept her from exploding then and there. Rarity couldn’t help but run her hoof over the slick shiny surface of her pvc catsuit feeling her little sister’s mess squish around under the pressure. There simply was no better feeling a mare could give herself.

As to how her little sister had gotten into diapers, Rarity didn't think she would ever be quite sure, but she suspected it had something to do with Sweetie Belle sneaking into Rarity’s bedroom as a filly and discovering things she should not have. A few years back after a bed wetting “accident”, a claim that Rarity was never fully convinced of, Sweetie Belle had suggested to Rarity that perhaps she should wear a diaper and have a plastic sheet out on her bed until she was certain she would not have another accident. Rarity had of course agreed to this suggestion, all the while somewhat suspicious of her sister’s intent but never speaking up about it. After a bit of hunting around in the basement she found her own old plastic sheet from the time she had wet the bed as a filly, and that afternoon she had managed to procure for herself some surprisingly well made diapers from a company in Canterlot who specialized in diapers for fillies too old for the standard cloth baby diapers and too young to fit into any of the adult brands. She had given the package to an oddly excited filly who promptly took them back to her room without saying a word more on the subject for the rest of the day. The next morning Sweetie Belle had shown up in Rarity’s bedroom wearing one of the diapers which was quite thoroughly soaked apologizing for having another “accident”, while also asking if Rarity could help her keep this between the two of them and not involve their parents any further.

This same set of events played out again the following day with Sweetie Belle coming to Rarity’s bedroom and asking for Rarity to hide her wet diaper for her. And again the same thing the next day, and the next, and so on. Eventually Rarity simply stopped waiting for her sister’s arrival and instead went directly to her room to retrieve the wet diaper. This process continued even after one day around a month later, when Rarity arrived to find that Sweetie Belle had not simply wet her diaper but messed in it as well. At first Sweetie Belle had apologized for it though she declined to give any specific explanation as to why she had messed in the first pace. Though finding Rarity surprisingly not angry about it, Sweetie Belle had begun to mess her diapers every night thereafter.

*** 5 years ago ***

As it was a rather unusually warm night in early autumn causing Rarity to feel no particular desire to sleep under any sort of blanket, she simply preferred to lay on her side with only her natural fur as insulation. It was not due to any excess heat or the fact that it was still a good two hours before her regular bedtime that kept her eyes wide open this night, no, it was that this time she was finally going to do something about the fact that her little sister insisted not only on messing a diaper every night but having her change her out of it then secretly dispose of it every morning. Rarity refused to continue to be used as nothing more than a glorified babysitter, or worse, a nurse, by her little sister. No, if Sweetie Belle insisted on continuing in her hobby, then Rarity was determined to get something out of it for herself.

At first Rarity had agonized over deciding weather or not to go through with her plans. What of Sweetie Belle told their parents? What if Sweetie Belle was disgusted by the idea and distanced herself from Rarity from then on? What if…? No, these doubts were not logical. Sweetie Belle wouldn’t tell their parents because it would be every bit as embarrassing for her as for Rarity, and Rarity could only think of one reason why Sweetie Belle so consistently used her diapers every night and was so secretive about the process. Her little sister had become sexually aroused by the act. And if she was aroused by what she was doing now, then there was little reason to doubt she wouldn’t at least be intrigued by what Rarity had planned. The sound of Sweetie Belle’s door opening between her bedroom and the bathroom that was shared between their respective bedrooms reached Rarity’s ears through the closed door on her side of the bathroom. Without giving herself any more time to second guess her planned actions Rarity called out to her sister.

“Sweetie! I need to talk with you!” Rarity said with enough volume so that Sweetie Belle could not pretend she hadn’t heard, yet quiet enough that it was doubtful her parents, walking around downstairs would take any notice.

The sound of Sweetie Belle’s door opening ceased abruptly. After a few seconds of silence Rarity was pleased to hear the sound of hooves coming across the bathroom floor towards her room. Sure enough, the door from Rarity’s room to the bathroom opened slightly letting light spill across the wood floor of her dim bedroom. Sweetie Belle’s head soon appeared through the opening followed by the rest of her. For just a second Rarity paused as she admired the filly’s cute round butt surrounded by her thick disposable diaper.

“Um, what is it Rarity?” Asked the filly, her voice squeaking slightly.

“Come over here Sweetie,” Replied Rarity, patting her bed with a hoof. “We need to have a bit of a discussion.”

Looking appropriately nervous, Sweetie Belle did as requested, her thick diaper crinkling slightly as she came over and then hopped up next to Rarity on her bed.

“Now see,” Rarity began, trying her best to sound confidant yet not angry at the same time. She had no desire to make her sister afraid, yet she had to put on this air of confidence so that Sweetie Belle would know that there was no room for negotiation.

“As you know, I do not mind that you wear diapers, nor do I mind that you use them for what they are intended for. However, what I do mind is the fact that I am having to buy these diapers, that you use, with my money, and that every morning I have to be the one who disposes of them –without our parents knowing- for you.”

“I am fully aware,” Rarity continued, “that as your older sister it is my duty to make sure that I help care for you, and love you, and try my best to make you happy. However, that does not grant you the opportunity to take advantage of me. And perhaps you might see how, given the things I mentioned, that I might feel as though I am currently being taken advantage of?”

Sweetie Belle’s ears drooped as she looked away from Rarity and shuffled uncomfortably.

“I’m sorry Rarity, I didn’t-“

Rarity scooted herself closer to her little sister and wrapped a foreleg around her slim diapered waist, cutting off her reply in the process.

“However…” Rarity continued. “That does not mean I am going to stop providing you with your diapers or helping you clean up after you use them. But it does mean that I am going to need to request a few things from you in return. The main thing being that if I am going to be the one buying diapers, then I should also be able to use them as well.”

Sweetie Belle's surprised stare up at Rarity was not unexpected.

"You...like to wear diapers also?" Sweetie Belle asked, her voice squeaking a bit again.

"You don't think that you are the only filly in Equestria who enjoys wearing a diaper and being able to simply go to the bathroom where ever they are? I have worn them in the past, which I think you know about... though it has been a while. I am aware of how nice they feel."

Sweetie Belle sat quietly for a moment at that and Rarity could almost hear the gears turning in her head.

“But, if you use some of them, and I use some of them…then we will use them up faster. And you will just have to buy more, so how does that save you money?” Sweetie Belle asked.

“As proud as I am that you made that deduction on your own just now, I can see that you misinterpreted my meaning. I never said that I would use my own separate diapers, I mean that we will both use the exact same diaper, every night. If I have to use the bathroom at night I will untape your diaper, go in it, and then tape it back up.” Well, she said it, now she just had to press her advantage.

“Uhh, Rarity?... That's really gro-“

“Now don't you say gross to me Sweetie Belle. You are the one who likes to pee and poop in your diapers on purpose and stay in that messy diaper with your poop squishing all over your butt for the whole night, each night. What I am suggesting doesn’t really make any difference. We are sisters after all, and this is the kind of thing sisters do for each other. And remember, these diapers are technically mine since I’m the one paying for them, so I can do with them what I want.” Rarity said with some force.

“I- I don't know Rarity, its just so… weird.” Sweetie Belle said looking over at the far wall.

“Not stranger than the fact you are using thoes diapers in the first place? I think you might just come to enjoy it.” Rarity continued.

“Besides, I know you are a bit envious about the things Scootaloo is getting to do with Rainbow Dash. Letting me use your diapers isn’t all that different from some of the things they do.

At the mention of Scootaloo’s not-so-secret, secret relationship with Rainbow Dash, Sweetie Belle blushed heavily.

“How do you know about that!? Or how I feel about it? Or-“

“Rainbow is one of my best friends Sweetie. Don't you think we get around to a bit of gossip every once in a while? I know a great deal about what goes on in this town, rather more than you realize, I believe.”

Rarity could see that her little sister’s resistance was crumbling under the realization that there really was no way out of the situation if she had any desire to continue to wear diapers. Rarity couldn't help but smile internally to herself with the realization that she had just made a big step toward her eventual goal of becoming Sweetie Belle’s first true girlfriend. This way she could ensure her sister learned about love and sex in all the right ways long before some other mare or Celestia forbid, a stallion, got in the way.

“Now, I do believe I mentioned that I had more than one ‘request’ to make.” Rarity said before her sister could change the subject in any way.

“If I am going to be able to use your diaper conveniently, then we will have to start sleeping in the same bed again. As you liked to come to my room and sleep with me quite often up until a few months ago, not long before you began to wear diapers, interesting that.” Rarity said almost to herself. “Then I do not believe this will be too much of an adjustment for you.”

“Now, since your bed is the one with the plastic sheet on it, I think I will in fact be the one sleeping in your bed from now on. I could move it to my bed, but then I risk having to answer some potentially awkward questions from mom and dad.”

“I uh, I guess…I don't really have a choice do I?” Asked Sweetie Belle.

“No, I don't suppose you do. I’m sorry if I am pressuring you too much but you need to learn that you can’t just keep taking from somepony without having to give back in some way eventually. Now I can see that its past your bedtime and that you’re tired anyway. It has been a long day after all, now I believe that its off to sleep for the both of us.” Rarity said while giving Sweetie Belle a gentle push off of her bed.

Making her set of conditions to Sweetie Belle at night when the filly was tired was of course part of her strategy, that way she would present less resistance. The last thing Rarity wanted was for the young pony to put up a fight about it and severely complicate the situation. Fortunately that hadn’t happened, and as Sweetie Belle yawned while Rarity followed her shiny smooth diapered butt back through their shared bathroom she congratulated herself on having planned out her timing so well.

As Rarity was climbing up onto the bed after her little sister, Sweetie Belle paused briefly.

“So like, do you have to go now, or…?”

“Well, aren’t we quick to get into the spirit!” Rarity said partially in jest. No, not at the moment, though that situation could well change in the morning.”

“Oh, ok. Well, um, I have to go, so… I guess I’ll go then?”

“Of course, do what you want.” Rarity replied quietly, smiling all the while.

Having been given permission, so to speak, and having no real other option, Sweetie Belle laid down onto the clear plastic bed sheet used for protection against precisely this sort of activity. To be honest Rarity had expected a bit more resistance to her involvement in her sister’s private life -the idea that Sweetie Belle was starting to be old enough to have a private life at all was a strange one- but Rarity was beginning to think that Sweetie Belle was beginning to enjoy the idea of being watched and touched while wearing and using her diapers. ‘She’ll become even more kinky than me some day, I guarantee it,’ Rarity thought to herself.

Rarity’s musings on the future were abruptly cut short as a soft hissing sound became audible in the nighttime stillness of the room. The front of Sweetie Belle’s thick diaper began to darken as an obviously large amount of pee, for a young filly, began to pour into it. Rarity couldn't help but smile down at the young filly.

“Here, let me feel.” Said Rarity as she reached her hoof between the filly’s back legs to press into the soaked padding to be found there. She rubbed up and down over the soft smooth plastic listening to it crinkle quietly. Sweetie Belle for her part, blushed slightly, but instead of resisting, she opened her legs even more widely to allow Rarity’s inquisitive hoof better access, all the while saying nothing. Obviously, Sweetie Belle liked what Rarity was doing, but was not in a mood to admit as much just yet.

“You really do enjoy these diapers don't you, sis.” Her remark really was not a question. It was quite an obvious statement but one that Rarity took no small amount of pleasure in saying. She really was fortunate to have a sister who was already this interested in exploring her sexuality even at this young of an age, even if Sweetie Belle was not at a point where she would think of her actions in such a way.

“Yaaaaahhhhhh….” Replied Sweetie Belle, her response turning into a yawn halfway through. “They’re pretty great.”

“Goodness, looks like somepony really is tired, well that makes two of us then. I think we should both be getting to bed soon, but first there is the matter that we discussed earlier. I need to pee, and there is a cute diaper in need of another good soaking right in front of me.

“So, should I take it off then? That will make it easier for you I guess.” Sweetie Belle said as her newly developing magical abilities began to tug at the diaper tapes.

“Oh, no need for that.” Rarity responded, her more powerful magic preventing Sweetie Belle from going any further.

“I’ve considered the matter, and believe that I have come up with a better way of doing this that won’t require you to take your diaper off every time. That is a rather awkward way of doing things after all.”

“Ok, here is how this will work, sit up and scoot forward a bit, there, just like that.” Now, I’ll position myself like so…” Rarity said as she turned herself around to face away from her sister and hiked her tail up so that her rear end was poised over and a bit in front of Sweetie Belle who was sitting up but leaning back on her forelegs. To minimize the chance that her stream of urine would miss the target altogether Rarity bent her back legs, lowering her rear so that her anus would be just at Sweetie Belle’s eye level. With a gentle pull of her magic Rarity tugged the front of her little sister’s diaper outward a bit forming a gap between the soft white fur of her stomach and the top of the diaper. With the diaper taped up nice and tightly this gap was rather small and provided less of a target than Rarity had considered. Perhaps using her sister’s diaper whenever she wanted to, especially in the middle of the night, was not going to work out very well if the two of them had to go through all of this to make it work every time. Well, she would think of something. Rarity’s first experimental stream was a little high, hitting Sweetie Belle right above her navel and splashing twinkling drops of urine all over her front.

“Oops, sorry. Here, lets try this…” Rarity said while Sweetie Belle gave her a somewhat annoyed look. Her next attempt was perfect and her now more powerful stream arced briefly through the air before disappearing with a faint splattering sound down inside the front of Sweetie Belle’s already wet diaper.

It was hard for Rarity to get a good look at her sister while peeing in her diaper, turned around as she was, but a few careful glances over her shoulder showed her a young filly quite enjoying herself as her eyes were closed and a smile curved her lips upwards. ‘Aha’, Rarity though, ‘she does enjoy this, seems like her earlier reservations will come to nothing then'.

Even though there was little light in the room, when Rarity turned back around to face her sister she could tell the little pony was wearing a quite thoroughly soaked diaper. She was actually rather proud of that diaper, it had not only been well wet in by its wearer, but had then managed to hold up while absorbing a fully grown mare’s worth of pee. Quite fascinating little bit of clothing that. Rarity decided that it might be worth her time to make a more detailed investigation of the construction of these diapers in her design studio.

“So, how does it feel? Rarity asked.

“Um, very warm, and kind of…heavy…” Sweetie Belle responded pressing a hoof into the thick soaked padding between her legs. “Its kinda nice…” She continued hesitantly.

“There you see, I knew you would enjoy it, even though its from me, the pee in your diaper doesn’t feel any different does it.”

“No, I guess not.” Sweetie Belle said happily.

The near giggle in her little sister’s voice was all Rarity needed to hear to know that she had just witnessed the creation of a future lover of pee and diaper play.

“But really now, we must be going to bed.” Rarity said before either of them could come up with new ideas which would put off bedtime until it was even later at night.

As the nights were warm this time of year the only thing Rarity bothered to pull over the two of them was a thin sheet. Nothing more was necessary, especially as Rarity couldn’t help spooning with her little sister. The temptation to have the warm, wet bulk of Sweetie Belle’s soaked diaper pressed up against her, just above her most sensitive areas was simply too much to resist.

“Good night Beautiful, I love you.” Rarity whispered as she kissed her wet little sister behind her ear.

*** The Present ***

The faint sound of a door opening a level below and on the far end of the penthouse accompanied by a faint “Rarity, I’m back.” Told Rarity that Sweetie Belle had returned from… wherever it was she had had to go off to in such a hurry. Rarity couldn’t really say she had been annoyed by her younger sister’s sudden unexplained departure. After all, if Rarity hadn’t found Sweetie Belle’s hastily abandoned diaper laying lonely on the floor of her bathroom, she wouldn’t be experiencing the pleasure of wearing it now.

Though the fact that Sweetie Belle was suddenly back, and Rarity, not only being in a position difficult to get out of, - How does a mare hide the fact she stole her younger sister’s messy diaper out of her own bathroom? – but being exceptionally horny due to the aforementioned diaper, decided without really realizing it, to reschedule her planned night time activities to this afternoon with the added benefit of a messy diaper she had not counted on possessing.

Mind made up, Rarity turned herself over and with surprising grace for a mare in an outfit both quite bulky between the legs and overall constricting hopped off her sofa and glided over to a large custom built hutch made of a fine dark wood which was a smaller version of an even larger one downstairs in the main kitchen. Opening one of the top drawers, Rarity removed a small nondescript metal container out of a number of other random items filling the drawer and from that container she removed a small light blue candy. At least it was made to look like a candy, the thing didn't taste as nice as a piece of candy ought to but the effect it had on a mare was even more sweet. At least in her opinion.

The supposed candy in question was actually the result of a joint project going on between her and her close friend Princess Twilight Sparkle. Even though as dear friends there was never any real reason for her to bother with thinking or even saying Twilight’s formal title, Rarity always took a bit of prideful pleasure at being able to call a true alicorn princess of Equestria a close friend.

In Rarity’s line of work, outside of the fashion industry that is, there is a very high demand for any mare who possesses, either temporarily or permanently, a fully functional male member. This ability almost exclusively tended to be the domain of unicorn mares due to unicorns possessing the most obvious active magical abilities. The problem was that any sort of true anatomy-modifying magic is extremely difficult to do correctly and requires great skill and practice. It was to Rarity’s great joy, then, when she found out from Twilight that alicorns, namely the four modern princesses of the known world, could preform this sort of magic with considerable more ease and with much better results than even an experienced unicorn.

It was even better knowing that the ancient magical process Twilight used had not only been greatly improved upon by Celestia in millennia past for the purpose of pleasuring her younger sister Princess Luna, but had then been adopted and all but perfected by Princess Cadance, the Princess of Love. Who better to make a great spell perfect than her?

Rarity knew first hoof just how great a spell it could be after being made to feel like a young filly again by being rutted hard with the thick shaft of an alicorn princess. Despite being hesitant at first Twilight had really taken to the role of using Rarity as her test subject for determining which variations of cock length, diameter, and even curvature were optimal.

It had been Rarity though, who had suggested that Twilight could prove invaluable at helping her find a way to allow even a simple unicorn mare to experience what it was like to possess for herself a hot thick shaft. It had taken over a year of development, more than a dozen trips to the Everfree Forest for magical plant specimen collection, and a few suggestions from Cadance to develop a powder that, when ingested, would grow a surprisingly functional and complete male reproductive system while preserving the full use of a mare’s natural female parts at the same time. So far they had managed to refine the process such that only a small amount of the power was necessary to maintain the effect for over a day. This then was the amount used in each of the candies which Rarity was so careful to keep inconspicuous in her drawer. It was not as though there were any known negative health effects of the things, but there was simply something about the idea of her gorgeous little sister having a cock and balls waving around between her legs that made Rarity somewhat uncomfortable. She preferred Sweetie Belle to maintain her purely natural and unmodified female form for now. There was a certain beautiful innocence, almost a form of virginity about it that Rarity was not yet willing to allow to be removed. Besides, Rarity felt it was important for any mare, especially for one as beautiful as Sweetie Belle to learn to love herself just the was she is. Only after learning to fully appreciate one’s natural beauty should a mare earn the right to start playing around at changing their physical form. That much Rarity believed anyway.

None of this however, prevented Rarity’s joy at being able to use her modified anatomy on her younger sister’s natural form.

With a single swift motion Rarity tossed one of the rare and extremely valuable blue candies into her mouth and swallowed. Smiling to herself she trotted out of the sitting room and over to her bedroom door which she eased open to gaze out down the hall with its plush blue white and blue diamond patterned carpeting and lighted alcoves filled with fine porcelain vases.

“Sweetie Belle, when you have a chance, could you be a dear and please come to my sitting room. I would like to have a talk with you.” Rarity called down the hallway.

“Um, ok, but give me a chance to make lunch first.” Came the reply from somewhere near the kitchen, Rarity thought.

“Of course, and thank you!” Rarity called back, closing the door again.

As she crossed the distance back across her large bedchamber to the sitting room again she couldn’t help but let a bit of a private grin show on her face as she began to feel the presence of her new and still growing stallionhood and balls squish their way into the sloppy mess filling her- no, her sister’s diaper. That combined with the shiny black pvc catsuit tightly covering her body made her quite certain she was going to enjoy this afternoon no matter what.

*** 4 years and 364 days ago***

When Rarity awoke she could immediately tell that it was still early morning. The color of the clear sky seen through Sweetie Belle’s bedroom window meant that the sun was just starting to climb above the horizon. Rarity did not usually feel so awake so early but she had gone to bed earlier than usual as well due to having to operate on her little sister’s sleep schedule. The next thing Rarity became very aware of was the presence of Sweetie Belle laying next to her on the bed. As expected, the both of them had shifted around in their sleep so they were no longer in the spooning position they had been in upon going to bed. However, they were still in contact. Rarity was laying on her back with Sweetie Bell laying on her side facing away from Rarity. Sweetie Belle was however laying right up next to Rarity so that her diapered behind was pressed up against Rarity’s hip.

The first thing Rarity realized as she became aware of the feeling of her sister’s diaper rubbing against her was that said diaper seemed to have a large soft bulge in it that she did not remember feeling when she had gone to sleep. The second was the smell. It was hardly overwhelming, but it was there. The definite aroma of a messy diaper. Rarity could feel her heart begin to beat a bit faster from excitement. Sweetie Belle had done just what Rarity had hoped she would; turn a wet diaper into a messy one.

Rarity shifted herself a bit to feel her hip press into and rub over the large pile of soft poop filling the back of the young filly’s diaper. Even such indirect contact felt so good. The next step then, was to reach her leg down and use her hoof to press into the full seat of Sweetie Belle’s diaper directly. She could feel the soft mess deform under the pressure and squish outward a bit from where it had all been.

Sweetie Belle stirred a bit and whispered a muffled “Good morning Rarity.” As her face was still partially buried in her pillow. Rarity decided that she really couldn’t resist any further. She could feel her increasingly sensitive pussy beginning to leak a bit of mare cum down her thigh, which was a good indication that getting back to sleep was an impossibility at this point. Though Rarity did pause a second and wonder how it was that she had gotten to this point. Was she really so turned on by her sister in a messy diaper of all things? A mare having a sexual attraction to her sister, while not the most openly discussed topic in Equestria, was hardly unheard of. Rarity supposed it was the juxtaposition of it all, a beautiful, healthy, filly living in a clean home with a nice family purposefully going out of her way to enjoy such a filthy smelly mess between her legs without any actual need to do so such as some medical condition. It just drove Rarity a bit wild. Perhaps her constant attention to professionalism, appearance, and sanitation in the rest of her life was proving a bit much for her subconscious to take. Something had to give, and diapers proved to be that outlet.

Rarity folded the rumpled sheet they were both still sleeping under back down to the end of Sweetie Belle’s bed. She was rewarded with the sight of her little sister laying on her stomach on top of the clear plastic bed cover, back legs spread open by a bulging bloated diaper so thoroughly soaked not a bit of padding remained dry. The diaper was mostly a slight yellow color but with an obvious brownish stain covering Sweetie Belle’s butt. Rarity’s state of excitement grew even more urgent as she considered what it must feel like for the filly wearing these diapers. Perhaps she should try to find some diapers in a size that would fit her some day.

Not being able to hold her desires back any longer, Rarity positioned herself over her little sister’s still sleepy body so that her dripping pussy was right over the thick wet and messy diaper below. With her heart thudding in her chest she lowered herself slowly down until her wet lips and clit made contact with the smooth warm plastic of Sweetie Belle’s diaper. She continued by letting her back legs fully relax, allowing her full weight to settle down on the soggy, dirty diaper. Rarity sighed with bliss as she felt the large mass of poop spread out inside her sister’s diaper from the weight of her body. Even through all the soggy padding Rarity could feel the squishy shit provide lubrication between Sweetie Belle’s butt and the diaper allowing it to slide around her backside more easily as Rarity began to rock back and forth.

“What are you doing Rarity?” Asked Sweetie Belle who was trying but failing to turn over due Rarity’s full weight keeping her in place.

Rarity now had her inner thighs pressing firmly against Sweetie Belle’s hips as she slid her wet slit up and down her sister’s messy diapered butt. It felt so warm and slick, a better sex toy Rarity could not imagine.

“I’m enjoying feeling your diaper. Doesn’t it feel nice? I know you like to mess your diapers so I don’t think this is much different.”

“I like it, it does feel…nice.” Sweetie Belle said as if trying to come to terms with the fact that she actually believed what she had just said.

“Don't worry about a thing dearest, just let your big sister make you feel good in your diaper.” Rarity said, now pressing her dripping slit against the poopy diaper and moving her hips about in small circles.

As Rarity’s hip thrusts against the messy diapered filly between her legs became more and more frantic, the smell coming from the diaper became even more noticeable. This only drove Rarity on to new heights of pleasure. Her only regret at this point was wishing she had decided to try this a few weeks earlier. No matter though, she would simply have to make up for lost time.

The feeling of having her clit in direct contact with Sweetie Belle’s beautiful diapered butt, the smooth warm plastic stretched tightly over the thick urine and poop filled diaper padding, not to mention the adorably filly wearing the wonderfully disgusting thing proved too much to allow Rarity to control herself. With a loud groan she came all over the butt of her little sister’s diaper, forcefully squirting clear mare cum between her inner thighs and the diaper between them. Even after cumming Rarity couldn’t help but keep going for a bit, smearing the clear sticky fluid all over Sweetie Belle’s diapered backside.

Panting, and feeling weak in all her legs, Rarity plopped herself down beside her little sister and gazed lovingly at the beautiful diaper that had just brought her to such an unusual but wonderful orgasm. Now the seat of the diaper truly showed what it contained. The once mostly light yellow color had been replaced by a shade of light brown that covered the whole of the back of the diaper. Rarity’s motions must have done a very good job of squishing that poop all around.

Being the young and fit mare that she prided herself on being, Rarity was not one to call it quits after only a single orgasm, especially not when she was this horny. Besides, after having cum her body had settled down enough to make her aware of a new and, due to current circumstances, welcoming sensation. As expected, it was time for her to make her usual morning poop, however on this occasion she had something wonderful planned for it. She was going to put her mess to an even better use than on thoes occasions where she collected some of her typically delightfully runny poop on her hoof and smeared it into her pussy. This morning however, her waste was going toward a higher purpose.

“Seems like you enjoyed that as much as I promised you would.” Rarity said to her sister as she rolled over onto her back now free of Rarity’s weight.

“Yah, that was fun! It feels really good in my diaper now, can we do that again?” The excited filly asked.

“Not the same exact thing no, but I have something even better planned.” Rarity said with a grin. This was going to be fun.

*** The Present ***

As Sweetie Belle crossed the plush purple carpet of Rarity’s bedroom and up the two steps separating it from the attached private parlor Rarity made sure that her sister got as good a look of her sleek black pvc encased body as she could manage, alternately stretching her fore legs, then hind legs, and arcing her back to thrust her padded butt into the air before settling down on her stomach. Legs outstretched in front of and behind her.

“Wow sis, your hot. As usual.” Sweetie Belle stated bluntly, not bothering to tread lightly around the mare who knew every secret she possessed, and who’s secrets she knew equally well.

“Complements are all well and good dear, but they won’t get you out of a talking to this time I’m afraid. Now, I have a keen sense of smell as you well know. Therefore, I was quite aware of what it was you were doing right before you left to go out with, Applebloom, I’m guessing?”

“Yah, it was her.” Sweetie Belle responded beginning to look a bit embarrassed as she realized the direction this discussion was going to be going in.

“And was this something you scheduled beforehoof?” Rarity inquired with a raised eyebrow.

“Yes, we planned it, but-“

“No buts.” Rarity interjected before her sister could attempt an excuse.

“Now, back to what you were doing before you left with Applebloom. Again, as I said, I have a good sense of smell, and can you guess where that sense of smell led me to only a few minutes after you left? Right to your bathroom. And before you complain about that, let me remind you who’s apartment this is. I own every room in this place and will exercise my right to enter any one of them at any time I choose. So, tell me what did I find in your bathroom?

Sweetie Belle fidgeted uncomfortably a bit but after a second of hesitation said; “One of my diapers.”

“Yes, One of your diapers, which I custom made for you.” Rarity replied.

“And tell me, what state was that diaper in?”

Again, more fidgeting.

“It was…used, wet and messy.” Came the younger mare’s response, minus any eye contact.

“Correct, wet and messy. Very, very, wet and messy. Just as it should be. However, I distinctly recall seeing you in the downstairs living room less than an hour before you went off with Applebloom, and I also distinctly recall that you were not wearing anything aside from that black rubber choker you are so fond of.

“This means, that all within less than one hour you put on one of the beautiful diapers that I made for you, used it very well, masturbated in it, -I see no other explanation for the sticky clear fluid mixed in with all the poop- and then took it off to go out with your marefriend for the afternoon. An event that you planned well in advance, which also means that you had no intention of wearing that diaper for more than, what, half an hour at most?

By this point Sweetie Belle was sitting down and her ears were drooping but Rarity was not finished.

“I know I’ve said this before but it seems that I will have to say it again, when you are wearing and using a diaper I made for you, you are wearing a gift from me, a symbol of my love for you. I am well aware that even the best diaper cannot last for ever and can only hold so much, but only wearing a diaper of that quality for half an hour is downright disrespectful both to the diaper itself and to the pony who made it, in this case, me!” When you choose to put on and use one of thoes diapers you are making a commitment that you will enjoy it for a whole day at least. I will accept nothing less. And if you can’t find it within yourself to enjoy my creations to the extent they were designed and intended for then I will stop making them!”

Despite being quite miffed, almost bordering on actual anger, the sight of her beautiful sexy sister sitting there with her ears flat against her head and tears forming in her eyes nearly broke her heart.

“Sigh… I’m sorry I raised my voice at you, its just that you should know by now how important this is to me, and anyway we have had this discussion before, so it bothers me that we have to have it again…”

“Fortunately for you, Sweetie Belle, the situation is not as bad as it could be as I happen to be a very resourceful mare. Here, have a look.”

As she spoke Rarity sat up on her sofa enjoying the squishing of the thick layer of her sister’s mess spread liberally between her legs and all over the newly formed appendage laying there. Once sitting upright, she reached up just beneath her chin to find the zipper tab concealed beneath a flap of pvc material and began to tug it down. The zipper line only extended partway down her chest and was designed to provide only the minimum available opening to allow a pony to put on and remove the garment. After all, one of the points of a good catsuit of any material is to be as seamless as possible. Rarity would never accept a zipper line that extended though the crotch, it ruined that smooth seamless appearance she was looking for.

Fortunately for the sake of appearances Rarity had spent time practicing getting out of the garment with the greatest grace possible. It helped to save face, especially in times like this. After using her magic to tug her last leg out from the outfit and carefully laying it out on the sofa, Rarity sat herself heavily back down with a wonderful squish and spread her legs to give her sister the best view possible.

“Now do you understand what I mean by ‘resourceful’?” Rarity asked the now smiling young teen mare before her.

“That’s my diaper, you’re wearing my used diaper…That is so totally gross, but kinda hot…” Sweetie Bell said blushing but not able or willing to look away from the extra bulky disposable diaper with light pink plastic covering and miniature versions of her cutiemark dotted around the top of the front. The way its absorbent padding was so heavily stained by the underlying goopy mess, apparent even through the diaper’s thick pink plastic was obscenely sexy, especially considering that the mare enjoying the mess was not the one who had created it.

“Yes, Sweetie Belle, it is. I have figured out a way of ensuring that you will receive a proper amount of enjoyment from this diaper. Now, quit your sitting around on the floor and get up here.”

Rarity guided her younger sister’s movements as she climbed up onto the sofa and over herself, as she was now laying on her back wearing only Sweetie Belle’s diaper with her head propped up on a cylindrical pillow. As soon as Rarity saw her sister’s rear positioned correctly she commanded Sweetie Belle to sit down. As the younger mare did so, her now wet, Rarity noticed, pussy and anus came to rest directly down on the front of her diaper. However, that was not the only thing they came down on top of. Rarity had to stifle a moan as her thick cock, already smeared in her little sisters’ shit was pressed down upon by the weight of a hot teen filly.

Sweetie Belle’s eyes grew wide as she suddenly recognized that she was feeling the presence of a large stallionhood under the surface of the bloated diaper. Rarity smiled up at her as she watched her sister’s reaction.

“You see, I think there are a few things you can do to help me out this evening.” Rarity said with glee.

*** 4 years and 364 days ago***

“The first thing I am going to do is untape the front of your diaper, but I’m not going to take it off you, just sit back and relax.”

Rarity quickly went about doing as she said she would, the moment the filly had leaned back into the pillow behind her. Her magic made swift and precise work of the four blue tapes on the front of the soaked diaper and within seconds Rarity was able to pull the thick wet padding forward with a light crinkling sound and let it plop down on the plastic sheet between Sweetie Belle’s legs.

For a few seconds Rarity simply sat and stared at the beautiful light pink slit peaking out from below her sister’s tail. While the filly in question was still too young for her to get wet with mare cum the urine matting down the fur between her legs also provided a glistening layer of fluid over thoes beautiful pussy lips that sparkled in the sunrise, this made for an equally enticing lubricating fluid. What made Rarity all the more excited was the presence of a thick layer of light brown poop with a somewhat runny consistency beginning to creep up from the bottom of the diaper. It was just beginning to come into contact with Sweetie Belle’s young slit.

‘Good’, thought Rarity. ‘Her mess hasn’t come up into the front of the diaper much yet. I’ll have more effect that way.’

“Now sit still Sweetie Belle, I think you will enjoy this.” Rarity said as she turned around and positioned her rear directly over her sister’s cute little slit. As soon as she felt her position was as good as it was going to get she released her control over her anus and was rewarded with a wave of released pressure as her morning poop rushed out of her and right into the front of Sweetie Belle’s waiting diaper with a soft ‘plop’. As she turned around Rarity could see that her aim was perfect as not only was the big soft pile of brown mess centered square in the middle of her sister’s open diaper, but it had landed partially on top of that beautiful pussy, now no longer visible, buried as it was under the huge pile of her her bowel movement.

The look on her sister’s face was an interesting mixture of fascination and disgust.

“Eww, Rarity, that's super gross, I didn’t know you were going to do that-“ Sweetie Belle said as she reached out a hoof to touch the gently sagging pile.

“Now, you just wait a second, wait for the next part before you get ahead of yourself.” Rarity said, blocking her sister’s inquisitive hoof.

Rarity smiled even more broadly as she slid both forehooves under the front of her sister’s diaper laying out on the bed and slowly lifted it up, pressing it into place against her and using her magic to once again securely fasten the tapes pulling the front of the diaper tight. Rarity knew she had won Sweetie Belle over as the the little filly closed her eyes and sighed as the huge mass of her older sister’s poop was pressed firmly against her and squished between her young delicate pussy lips.

‘Sweet Celestia’, Rarity thought, ‘that was beautiful. I just might have to try that for myself.’ She shuddered internally at the unquestionably disgusting thought, but somehow, after seeing her sister enjoy it, it didn’t seem so bad. And besides, what kind of sister would she be if she did things to her younger sibling that she wasn’t willing to do to herself?

Before she could really stop to consider what she was doing, Rarity couldn’t help but act on a sudden impulse to bury her face in the bulging, stained, poop filled front of her little sister’s diaper. Sweetie Belle let out a little squeak of surprise and then a giggle of laughter as Rarity alternately kissed and licked the smooth plastic crotch of the extra messy diaper. The smell was awful, but that just made Rarity’s pussy leak cum down her inner thighs all the more.

As she pressed her muzzle and tongue against the slick plastic of the filly’s diaper, Rarity could feel the pressure she applied spreading and squishing the mess around underneath. It was driving her a bit crazy she admitted. She had already cum on the back of this diaper, perhaps she could do the same for the front? Though she wanted to do something a bit different this time. Besides, it simply wasn’t fare for her sister to be enjoying all this mess for herself. As usual with Rarity, inspiration struck. Telling her sister to stay where she was. Rarity leaped off the bed and hurried back through the interconnected bathroom and into her own room, not seen since the previous night. As she was a well organized pony, Rarity had no trouble locating precisely what she was after.

Returning to her sister’s bedroom with one of her favorite pairs of shiny black rubber panties, Rarity was happy to see Sweetie Belle enjoying pressing her hoof into the heavy, now somewhat flattened out, bulge in the front of her diaper. Even though the little filly probably couldn’t achieve orgasm yet, something Rarity really ought to test one of these days, she was still obviously making herself feel good through the thick padding. Without wasting any more time Rarity hopped back up onto the bed.

“Here, let me help you with that.” Rarity said as she reached out her foreleg, pushing her sister’s own aside. Starting from the bottom of her sister’s crotch, Rarity applied more pressure that she would have needed if simply rubbing was her goal, and pressed upward. Pressing her hoof upward, Rarity was pleased to see a bulge of poop pile up under the diaper ahead of her moving hoof. When her hoof neared the top of Sweetie Belle’s diaper the bulge squished its way out the top of the diaper and onto Rarity’s waiting hoof. The process left an obvious brown smear along the top edge of her sister’s diaper and in the fur around her navel.

“Why’d you do that?” Sweetie Belle asked, “I don’t want to make a big mess…”

Rarity gave her a ‘bit too late for that’ look but didn’t say anything.

“I meant outside of the diaper!” Sweetie Belle said blushing slightly.

“Don’t worry sis, that’s all the mess I need to make, at least so far as you’re concerned.” Rarity said smiling more to herself than for her sister’s benefit.

Taking the big glob of her own poop that until then had been so comfortably sitting in her sister’s diaper, Rarity began to smear it all around the inside of the crotch of the tight rubber panties that she held open with her magic in front of her.

Understanding dawning on her face Sweetie Belle began to giggle as she watched her older sister trying to get as much of her mess as possible off of her hoof and into the inside of her panties.

“Hehe, you like the feeling of poop on you too! I knew it! You’re jealous of my messy diaper aren't you?” Sweetie Belle asked still giggling.
Why was it that siblings could be at their most perceptive only at times when that perception could cause the greatest embarrassment? Rarity asked herself, trying not to make eye contact with the laughing filly.

“You’re one to talk.” Rarity grumbled, wiping the remaining mess off her hoof and onto the front of her sister’s still bulging diaper.

While the still smiling filly watched, Rarity delicately took the rubber panties with their now very messy crotch and pulled them up her back legs being careful to not leave any obvious streaks of poop up the white fur of her calves. The feeling of having the pile of now slightly cool moist shit squish itself into her dripping pussy was every bit as awful and as wonderful as she had hoped it would be. No wonder Sweetie Belle liked her diapers so much, Rarity couldn’t think of any other lubricant she could apply to her lower lips that would feel half so good.

Shuddering from the intense sensation of the tight smooth panties hugging her hips and butt, not to mention the mess they held pressed tightly against her, Rarity laid down on her back and scooted her butt forward until the black shiny tight crotch of her messy panties made contact with the stained off-white thick bulge of her sister’s diaper. Moving forward a bit more made her little sister’s diaper press firmly between Rarity’s legs and squished the mess around in both of their respective garments.

Rarity moaned as she felt her shit being forced between her dripping lips and around her clit. How she was supposed to ever fully clean herself up after this she didn't know, but at the moment she didn't care. Normally Rarity prided herself on being a mare in full control of her body, when she came it was precisely when she wanted to, and not before. But this time everything was so new, so stimulating, so nasty, and so erotic. It wasn’t just sex with another mare for money this time, though she would never say she didn't enjoy such things, it was just all so new. If it hadn’t been for meeting Princess Cadance two years ago and being shown just how diverse pony sexuality could be, she would never have been suspicious of Sweetie Belle’s desire to wear diapers, which meant she would never have gotten to this point in her relationship with her sister.
As the intensity of her shit smeared orgasm overcame her, she groaned loudly feeling the brown slop work its way up her vagina. As her cum splashed out into the crotch of her tight rubber panties, some back part of her mind decided that she would have to thank the Princess of Love some day for this when she got the chance.

‘No better than some dumb stallion.’ Rarity thought to herself as the blinding pleasure of her orgasm died away. She hadn’t been rubbing her pussy on her sister’s diaper for even a single minute before she lost control. If it felt this great without even wearing a diaper and only having a hoof full of poop in her panties how good would she feel with her entire crotch and butt swimming in the stuff, surrounded by thick pee soaked padding? Right then and there Rarity resolved to herself that she would either find, or make, quality disposable diapers in a size that would fit her. And the next time she had a session with her sister like this the both of them would be well padded and totally messy.

The current situation though, was far too stimulating for only a single orgasm to suffice. In no way could she be finished. And besides, Sweetie Belle sitting there, back legs outstretched before her and thick shit filled and smeared diaper taped tightly around her waist squishing two hot loads of poop into all her best places, was simply too adorable and hot to resist playing with.

Making the filly squeak in surprise, Rarity lifted her completely off the bed in a gentle yet firm magical field and set her down so she had both sets of legs on opposite sides of Rarity’s head. Gazing up at the underside of her sister’s filthy diaper Rarity licked her lips in anticipation.

“Please Sweetie Belle, do your sister a big favor and sit down on her face in that lovely diaper you have on, its so beautiful.” Rarity said quietly as she reached up a hoof and gently stroked the brown stained, bulging crotch of the diaper hanging over her.

“Um, ok, here goes…” Sweetie Belle said, giggling again. What a wonderful sound that was for Rarity, nothing was better than a happy sister.

As the filly’s diaper, now little more than a thick poop and urine filled bag pressed itself down, covering Rarity’s eyes, and nose, and rubbing against the hard shaft of her horn, Rarity smiled in the darkness under the squishy, smelly padding and decided, as Sweetie Belle began to rock backward and forward in her mess, that she had the best little sister in the world.

*** The Present ***

Rarity watched on happily as her young teen sister came with a rather un-feminine yell while sliding her wet slit up and down the length of the long bulge Rarity’s cock formed in the front of her diaper. No matter how thick and wet the padding, her hard stallionhood always easily had sufficient girth to become notable through her diapers. Or in this case through her sister’s. Feeling her sister’s weight slide along her shaft with Sweetie Belle clamping her inner thighs around Rarity’s padded hips was such a wonderful feeling Rarity simply wanted to squirm in delight like a little filly.

“Now see, and here I was starting to believe you didn't like your own diapers.” Rarity said in a gently mocking tone.

Sweetie Belle stabbed her sister with a reproachful look while panting from her prior exertions, but declined to escalate the discussion with even more intense sarcasm.

“Its, not just your- my- diaper that I’m enjoying, you have something underneath that you know I very much want to have.”
Rarity grinned like a cat with the proverbial mouse.

“Oh, do I?” Rarity asked with rather insincere confusion. “Well, if you want it so much would you at least like to see it? I’d love to show it to you.”

Sensing that Rarity was not about to take no for an answer to her question and having little if any desire to respond in such a negative manner herself, Sweetie Belle scooted backward off of what used to be her diaper. As soon as Rarity was free of the overlying weight of her sister she began to slowly remove each of the diaper tapes individually, drawing out the process as a way of teasing her expectant sister.

As the last of the tapes released their hold on the front of the diaper, Rarity peeled the extra thick padding back allowing her throbbing cock to stand up high and proud. The normally smooth creamy white skin of her dick and equally shiny black skin pulled tightly around her heavy balls were each fully coated from head to base in a liberal covering of runny, light brown shit that slowly dripped down the length of Rarity’s long thick shaft, glistening in the evening sunlight. The sudden exposure of her wet stallionhood to the cool air of the penthouse made her shiver and her throbbing pussy, hidden under her heavy balls, began to leak even more.

The now unfolded diaper was a virtual sea of goopy light brown muck and it made Sweetie Belle wet just imagining how it must feel to have had both a pussy and cock surrounded and coated in so much beautiful scat. Then she realized again with a start that what she was looking at was her own mess in her own diaper from just that afternoon. And indeed she again felt guilty at having abandoned such a wonderful mess, even if it had been to go out on a date with Applebloom. Had she really pooped and peed so much as to result in this? Had Rarity added to it?

“Take a good look Sweetie Belle. This is all yours, I haven’t added a thing to this diaper… yet.” Rarity said, gesturing to the general mess, even as her teen sister held up a foreleg across her muzzle in a futile attempt to relive herself of the stench, which she was starting to think would burn the inside of her nose. Sometimes she wished ponies didn't have such a good sense of smell.

Despite her reaction, Rarity was proud to see her sister smile from behind her leg. Sweetie Belle was the love of her life and being able to please the constantly horny teen was an endless source of pride for her. Besides, there was no way in Tartarus she was ever going to let her pure, innocent, technically virgin, sister get anywhere near a true stallion until she was ready to settle down and take the time necessary to properly help raise a family, a time that was hopefully at least twenty years away. And even then, Rarity would rather her sister find a nice mare to settle down with, like Applebloom, besides, with the magical knowledge of this modern day and age a male pony was not strictly a prerequisite for having a foal any longer. The only pony who had functional male equipment that she was going to let Sweetie Belle get anywhere near was herself. Though perhaps letting her dear friend Twilight, or even her recent sexual mentor Princess Cadance, have a go at the teen filly’s wet slit would be fun to watch. She still wasn’t convinced Cadance could fit though.

Movement from Sweetie Belle brought Rarity back out of her thoughts, and she watched the younger pony stand up and move herself over Rarity, or more importantly, over her hard, shit smeared shaft and then line herself up properly.

“Um, may I?” asked Sweetie Belle as she realized, blushing, just how forward her actions seemed.

“Do you think I went to all this trouble only for you to see it briefly before I hide it away again in my- your- diaper? Hardly, I want you to, beg you, to fuck your gorgeous body with it as much as you can stand. Please, go ahead, its all slimy and lubed up with your own mess, you can’t find a smoother ride than this in all Equestria!”

Laughing, Sweetie Belle did as was suggested and set her pristine, glistening, light pink slit right on the tip of Rarity’s cock, smeared in the scat of the filly who was going to fuck herself with it. ‘What beautiful irony’ Rarity thought at the scene before her. Relaxing the muscles in her back legs, Sweetie Belle eased herself down the long thick girth of Rarity’s shaft. The feeling of being so completely filled and having her own slimy mess act as the lubricant between the already smooth skin of her older sister’s dick and her wet vaginal walls made both her and Rarity moan continuously through the whole process. Rarity only felt her sister stop sliding downward when she realized the tops of her balls were being squished up against Sweetie Belle’s anus. Even though it was not the first time, Rarity was so proud that her sister had the capacity to take the whole thing inside of herself while remaining so wonderfully tight. Truly the capabilities of the teen pony’s muscles were a wonder.

For the first minute they both simply stayed still, enjoying being connected at such a basic level. For Rarity, a mare, to know what it was like to be inside her own sister. Well, that was truly a gift handed down from Great Faust, or perhaps from one of the lesser Elder Gods. Twilight would undoubtedly know, ancient religions were among her many interests. When Sweetie Belle began to lift herself up and press back down all thoughts of near forgotten faiths fled Rarity’s mind. With the right consistency, scat really could be about the perfect lubrication for sex, mixed with a bit of urine the result was a wonderfully slimy and slick glistening paste that felt unbelievably good when in contact with any sexual organ. That’s what made wearing a messy diaper for long periods such a joy. Doing so, she could practically bathe her nether regions in the stuff all day, which kept her feeling gloriously horny for much longer than she otherwise would have been able to.

Sweetie Belle’s increasingly swift pumping up and down on Rarity’s thick cock was making coherent thoughts difficult. With each downward push Sweetie Belle made a different kind of grunt or squeak and the force of the motion made Rarity’s butt audibly squish about in the thick layer of her sister’s mess in the back of the diaper. Rarity could be a bit of an aggressive mare both in daily life and in the bedroom, or wherever she chose to have sex, so it was nice every once in a while to simply lay back and let her sister do all the work. Rarity enjoyed watching her little sister’s shit smeared pussy lips glide effortlessly up and down, eagerly taking in the entirety of Rarity’s hard shaft. And with each downward thrust of Sweetie Belle’s hips the sudden contact of her butt with Rarity’s crotch made a loud slapping/squishing sound that she found quite naughty.
With her front legs holding onto Sweetie Belle just above her hips, Rarity was able to guide her little sister into a circular pumping motion not unlike the movement of the coupling rod on the wheels of a steam locomotive. After only a few minuets of this, Rarity was reaching her limit, she could feel the wonderful pressure building at the base of her dick as Sweetie Bell’s hungry pussy once again fully engulfed the thing.

“Oh Sweetie, dear…I’m almost there… I going to cum inside your sweet body.” Rarity moaned not having the breath necessary to properly speak her words.

“Please sis…cum in me so hard…” Sweetie Belle replied equally as breathlessly.

Rarity didn't need any more excuse than that, as she felt her her cum flow up her rock hard shaft and erupt out her head as it pumped thick ropes of creamy white fluid that splashed against her sister’s cervix. More and more cum kept squirting out of her until it began to squish out around Sweetie Belle’s pussy lips and the base of Rarity’s cock. At some point while Rarity had been lost in orgasmic bliss, her younger sister had came too, squirting out a spray of clear slightly sticky fluid that mixed with the brown scat spread all over to drip down and over Rarity’s large smooth black balls.

Rarity didn't think she had ever been able to sustain an orgasm for quite so long before. Certainty this was not the first time she had fucked her little sister with her own stallionhood, nor was this the first time doing so while her cock was coated in the contents of a messy diaper, but it was the first time said diaper and contents had previously belonged to her sister. That brought the intimate kinkiness of the whole endeavor to even greater heights.

Having finally spent all her energy on top of her older sister’s cock, Sweetie Belle had fallen forward and was now comfortably laying on Rarity’s chest with her horn tucked under Rarity’s chin. Fortunately for Rarity, this position had allowed her still solid shaft to remain buried deep into her sister’s hot wet vagina. Rarity knew just how to take advantage of such a situation and she had prepared for it well by not using the bathroom for some time before her little sister had returned home. While in the throws of passion the urge to urinate had all but disappeared, but now it came back with almost painful urgency.

‘Alright bladder, this is your time to shine.’ Rarity thought as she fully relaxed herself. Almost immediately a hot torrent of piss rushed up her hard cock and exploded against Sweetie Belle’s cervix, just as her cum had minutes before, with such force Rarity could hear it through Sweetie Belle’s body.

Sweetie Belle instantly opened her eyes wide as Rarity’s hot urine gushed into her vagina and began to squirt out around the base of Rarity’s cock making a warm cascade around her balls and over her anus before disappearing into the layer of warm shit and diaper padding beneath Rarity’s well rounded ass.

Rarity had no fear that her sister would be angry, as this was not the first time she had pissed into her sister after sex, but she was surprised at how the teen mare, so calm and quiet before, sat back up as quick as she could blink and began feverishly fucking herself on top of Rarity’s still pissing dick, sending droplets of urine splashing about all over.

In only a minute the half crazed filly had brought them both to orgasm a second time making Rarity extremely glad she had done what she had planned to do. Apparently cumming only once was no more acceptable an outcome to Sweetie Belle than it had been for herself.
Several minutes later, Rarity found herself sitting upright working on taping her sister’s now much more thoroughly soaked diaper back up tightly around her waist and still hard cock. It may not have been as exquisite a feeling as being buried balls deep in her own little sister, but having her cock once again squishing firmly into the thick layer of scat covering almost every part of the inside of said sister’s super messy diaper was heaven in and of itself.

“Ugh.” Muttered Sweetie Belle sitting opposite Rarity at the other end of the sofa. She had her legs spread wide open and was pushing a hoof experimentally at her pussy.

“My pussy is going to smell awful for the next week.” She groaned as she watched a few more drops of brownish fluid leak out and disappear underneath her butt.

“Oh, but that’s all part of the fun!” Rarity said as she completed adjusting her sister’s messy diaper around herself.

“It will keep reminding you of what we did this evening, and that will keep you feeling horny.”

Looking up from her leaking pussy Sweetie Belle raised one eyebrow at Rarity yet said nothing.

“Well, if you don't like it I’m sure there is some magical ways to get your insides thoroughly cleaned up but where’s the fun in that? Having a pussy that constantly smells like a messy diaper is one of the better pleasures in life and will show you who your true friends are when they go to lick it.” Rarity said with a shrug.

Sweetie Belle could only laugh and shake her head. Even after all they had done together Rarity’s kinky side still managed to surprise her.

“So.” Rarity said while looking up, suddenly sounding a bit more serious than before.

“I know that for some time now you have been wanting to accompany me on one of my nightly excursions about Canterlot, see what all the city has to offer and all that. I’m not going to take you just anywhere, there are certain types of fetish clubs which even I don’t want to go to, and some I’m not even allowed in, but if nothing else there are a number of mares who I think you should get to know, and who want to get to see you. I know that for a fact. After seeing you so willing to enjoy everything we did today, and having given you a rather memorable lesson in responsibility at the same time, I think you’re ready for a bit of a night out on the town. I for one am going to be going out while wearing your diaper, under a dress of course. Now don’t you start to be embarrassed by something like that Sweetie Belle.” Rarity said as she saw her sister begin to grimace at Rarity’s intended choice of public clothing.

“Remember, the fewer things in life that embarrass you the more opportunity you will have.”

“Now in you’re case Sweetie Belle, I want you to be in something a bit more form fitting than a diaper.”

With that Rarity levitated a plain white package out from behind the sofa where she had obviously had it hidden for the whole afternoon just for this very moment and held it out in front of her sister.

“From me to you Sweetie Belle. I won’t have you meeting any of my associates or clients on your first real night out without wearing something I made specifically for your beautiful body.”

“Wow, really, Rarity! Thank you! Thank you!” The teen filly said standing up and hugging her diapered older sister.

“And you really mean it? We can go out together tonight? This is so awesome…even if you do insist on wearing my diaper.”

Rarity smiled and nodded her head in conformation as her younger sister carefully took the lid off her new gift. Inside was a short dress where the top was made of good quality super shiny and slick black pvc plastic. It had wide shoulder straps but no sleeves and came down to the front of Sweetie Belle’s hips, the skirt part of the dress was very short, only just reaching the base of her tail and made of a thick transparent clear plastic that made a nice rippling sound when handled. This transparency allowed anypony to see through to her cutiemark and also to the included tight form-fitting shiny black pvc thong, a thong like the dress, that Rarity had custom made to not only fit her younger sister’s beautiful thighs and butt, but also to tightly wedge itself into her pussy thereby enhancing the overall stimulation of wearing the dress. While ponies typically went about their daily lives wearing nothing, and it was also typical to keep one’s tail down to prevent making more of a display of oneself than intended, wearing clothing was usually taken as something either for a very formal setting or for the purpose of enhancing one’s sexuality. In the case of Sweetie Belle’s new dress, the intent was very clear and the transparent plastic showing the tight thong underneath would erase all doubt. Besides, the thong forced Sweetie Belle to keep her tail raised to stay more comfortable, which only added to the subtle yet unmistakably erotic nature of her outfit. Almost as an afterthought a plain black pvc choker was also included in the box.

Sweetie Belle’s eyes began to tear up as she looked from the dress to her sister and then back again. Not only would this dress and thong make her look unbelievably hot but she could wear it for Applebloom and Scootaloo and perhaps get to have a good threesome again like they used to. A gift like this required a proper thank you and so, box held up in her magic, Sweetie Belle darted forward and kissed her beloved older sister hard on the lips.

As their tongues wrestled together, sliding into and out of each other’s mouths. Rarity knew that she had made all the right decisions and that now she was ready to share her precious little teen sister with the world.