A Helpful Sister

by Ragabash

Rating: mature
Tags: Slice of Life, My Little Pony: Friendship is Magic, Rarity, Sex, Sweetie Belle
Length: 2465

After a spell gone wrong, Sweetie Belle ends up with an additional body part. Rarity helps her in dealing with it.

After a small magical accident, Sweetie Belle ends up with an organ, that normally only colts have, and a heightened libido. But thanks to her big sister's daily assistance, it's only a small problem.

Until one day, Rarity's mouth isn't enough...

Contains, Foalcon, futa and incest. You have been warned.

Published 2015-12-26 14:30:02 UTC
Last updated 2015-12-26 14:30:02 UTC

Chapter 1

Rarity arose to another ordinary morning. An ordinary morning of a rather extraordinary kind. Since over a month, her daily life was pretty odd. Some might find it downright disturbing. Rarity, however, didn't have any complaints about it.

The white unicorn got up from her bed and left her room. Before, the first thing she would have done is take a shower. Now, however, it was better to leave that for later. Otherwise, she would need another one.

As she walked through her house, anticipation built up in her. Even a month after, it was hard getting used to it. Part of her didn't even want to get used to it. It was something special and should remain that way. For as long as it remained.

Rarity stopped, just as she was outside Sweetie Belle's room. A bit nervous, but without hesitation, she knocked on the door and, without waiting for an answer, went inside.

The sight that she got would have shocked anyone else. Indeed, the at first she was pretty startled herself. But after all the time, it didn't really faze her anymore. At least, not on a negative way.

Her little sister was lying in her bed, wide awake. She seemed kind of... distressed and her cheeks were flushed. The reason for that was on her lower body. The blanket above her had a large bulge, which one wouldn't expect considering her age and sex.

With her magic, Rarity quickly moved the blanket aside, revealing Sweetie's decidedly non-filly part. It was indeed a large penis, that stood erect upwards, as if it was waiting for something, while two testicles below obscured her true sex. Its dark gray color contrasted with Sweetie's white coat.

It was over a month ago, that an accident at Twilight Sparkle's library gave her this colthood. All she was supposed to do was practice her magic and even the princess wasn't sure how she could mess up that badly. While it was certainly awkward for several ponies, they were lucky that this was the only effect. Rarity didn't want to think of what else could have happened.

Well, something else did happen, actually. Not only did the filly get a body part she wasn't supposed to have, she also got an... appetite, that was very inappropriate for her age, even rivaling several stallions in that regard. Being the caring sister that she is, Rarity decided to help her out with it. Every day, in the evening and the morning.

At least, until Twilight found a way to get rid of that misplaced penis.

Smiling, Rarity approached her visibly aroused sister. "Good morning, Sweetie," she greeted her cheerfully, as if nothing strange was going on. "I hope you slept well."

"G-Good morning, Rarity," the filly replied. She was less concerned with how she slept and more with her erection.

The mare placed one front hoof on the hard shaft, making Sweetie jump a little. It didn't seem like she put hoof on herself. At least, not much. That was good. Rarity couldn't just leave her by herself. An inexperienced young thing like her couldn't please herself properly.

Nor could anyone else than her big sister, for that matter.

Holding the shaft between both hooves, Rarity pulled it closer to her. As she did several times before, the mare engulfed the head of the penis with her lips and slowly moved down the length. Sweetie, really in need, already began to moan loudly. Encouraged by that, Rarity began to move quickly up and down, her lips rubbing over the sensitive skin of the shaft.

Soon, Sweetie began to twitch at the sensations her sister gave her. Even after all the time, she didn't get used to it and reacted strongly to these pleasurable feelings. Going a bit further, Rarity took more of her cock in and licked all over the length.

Sucking her sister off and listening to her moans excited Rarity, but she resisted the urge to touch herself. Her only purpose was to please Sweetie. For now, at least.

It's not like she had to wait very long. After only a short time, the young filly moaned louder than before, while her body stiffened and a fluid began to shoot out of her cock and filled Rarity's mouth. Being a good sister, she didn't stop sucking on her and swallowed Sweetie's cum diligently.

Only when she drank the last drops, Rarity let go of her and backed away, letting the, now semi-erect, shaft leave her mouth. Afterward, she went up to her exhausted sister and gave her a little kiss. "I hope you enjoyed it, Sweetie," she said, before she left her, so she could recover from her orgasm.

Also, she really needed a shower now.

Noisily, the hot water was pattering on Rarity, running down her entire body. However, she wasn't concerned with cleaning herself right now. Her thoughts were still with her sister and the penis she just sucked off. Letting any inhibitions go, the mare was sitting on the floor of the shower and rubbed her pussy rapidly. She didn't try to suppress her moans. It's not like it really mattered if Sweetie heard her or not.

It was moments like these, that she was more honest with herself. That she didn't please her sister solely to help her. That she loved her big cock. That she wanted to... play with it more and feel it inside her. But part of her was hesitating to take that step. After all, Sweetie was still a foal and her sister.

Suddenly, Rarity could hear the sound of the door opening. She was startled, but soon figured that it had to be Sweetie. Did she hear her moans?

She was startled even more, when the shower curtain was moved aside quickly. Sure enough, her little sister stood there. For a moment, she wondered why she acted so rashly, but soon she could see why.

Sweetie was blushing heavily, however, it didn't seem to be due to embarrassment and more due to arousal. Between her legs, Rarity could see her cock, completely erect as if her climax never happened. The hole on the tip glistened wet and some pre-cum dripped down onto the floor.

"I-It's not enough...," the filly said weakly.

That much was obvious. But it was strange, she wasn't so needy before. A blowjob in the morning was enough. Until the evening, at least. Did the effect of the misfired spell get stronger? She would have to ask Twilight later.

For now, she had to deal with her overly horny sister. And her own horniness. Seeing Sweetie like that... It made it really tempting to go all the way. Her legs were jittery, as if she had trouble standing because of her arousal, and she was breathing heavily.

"Rarity, please..." she pleaded, without saying for what.

She seemed to be even hornier than before. Rarity wasn't sure whether giving her another blowjob would even work or whether she'd go back to being unsatisfied. Maybe even more than before. There was really only one thing she could think of, that might help.

Rarity stood up and turned around. Lowering herself a bit, she presented her backside. Sweetie didn't hesitate to mount her and pretty sudden, the mare felt her little sister on her back and her hard cock poking through her nether lips. Rarity yelped in surprise. She didn't expect things to go that fast. Maybe Sweetie also gained the instincts of a stallion. Maybe she was guided by her arousal.

What it may be, it led her well. Without a need to accustom herself to the unfamiliar situation, the filly moved her hips quickly back and forth, thrusting her cock frequently into her sister. While it was odd at first, Rarity quickly got used to it and enjoyed the feeling of her shaft rubbing over the inner walls of her pussy.

Both sisters moaned loudly and nearly in unison, as the filly pounded the mare. Neither cared about the water falling down on them, wetting their bodies.

Sweetie held out much longer than Rarity thought. She plowed into her with no end in sight. At this rate, she might even be able to endure it to the end and satisfy her sister. Rarity didn't want to get her hopes up too much, but that thought didn't leave her mind, once it was there.

"You're doing great, dear..." the mare said gently. "Keep it up and... You'll get a little reward."

She wasn't sure whether Sweetie, who was absorbed into plowing her, even noticed what she said. In general, she wasn't sure how to handle her overly horny sister. But it couldn't hurt to talk to her.

"If you... fuck me well," she continued. "Then this, won't be the last time..."

It seemed that she was getting through to her, as Sweetie's movements suddenly got faster. As if she wanted to impale the mare, the filly thrust her hard rod into her with as much force as she could muster. Her moans were heavy, as if she was really turning into a stallion.

Rarity bit her lower lip, as Sweetie relentlessly rammed her. Despite being so young and inexperienced, she was better than most stallions she did it with. And those weren't just a few. The mare had a bit trouble to keep herself on her legs, but didn't try to stop her sister. It's been a while, since she was fucked that well and she wanted to enjoy every second of it.

But she couldn't do that for long. Maybe it was because her last time was a while ago or maybe Sweetie was just that good, but she soon got to her limit. She still didn't ask the filly to slow down, instead opting to just let it happen and let her sister get the victory that only painfully few stallions got.

Letting out a loud moan, in which she put all the lust and relief she felt, Rarity embraced the huge wave of pleasure that gripped her body. The water that ran over her body and the remaining thrusts, her sister was giving her, only intensified the climax, that nearly seemed to go on forever.

Sweetie couldn't endure it anymore either. While her big sister was coming, she was also driven over the edge. With a mix of a moan and a grunt, she plowed hard into Rarity's pussy, without pulling back again, and released her seed deep in the mare, as if she tried to impregnate her. The filly wasn't even sure if that wasn't exactly what she wanted. She only knew that she had to had to come into her sister.

Like that, the two sisters shared their orgasms, lost in their pleasure while hot water poured over them. It didn't seem to end, yet at the same time, it was over way too fast. Afterward, Rarity and Sweetie Belle were left behind breathing heavily.

"W-Wah!" The filly suddenly pulled away, her softening cock sliding out of the mare's wet pussy. She was slipping on the shower floor and fell down on her butt, although she didn't seem to care. She looked up at her sister with a thick blush on her cheeks. "I-I-I-I...," she stammered, barely able to say anything. "I.. I'm sorry Rarity!" she finally blurted out. "I-I don't know what came over me and..."

The mare couldn't help but chuckle at her little sister. It was kind of amusing how her behavior could change so quickly, after she got release. But Rarity knew very well what arousal could do to a young thing like her, especially when that feeling was still new.

With a warm smile, she approached her sister and gave her a kiss on the cheek. "It's alright, Sweetie," she said calmly. "You did very well today. I wasn't satisfied like that since a long time."

The filly didn't seem to be sure how to react, but she started smiling too, although the blush still made it clear how awkward she felt. "Uh... You're welcome?"

"No need to be ashamed, darling. It's perfectly normal to do feel such urges and to act on them." Well, maybe it wasn't so normal for a filly to have a penis and to do it with her sister. "It's rather... dirty, I admit, but not in such a way that you have to feel bad about it."

Relieved, Sweetie calmed down. She really thought that she did something wrong and was glad that this wasn't the case. But something still burned in her mind. "Rarity?"

"Yes, Sweetie?"

"Um... About something you said earlier... Can we... Do it again?"

Rarity wasn't exactly a troublemaker. Not like Pinkie Pie or Rainbow Dash. As such, one wouldn't expect her to be involved in something nasty. At least, not out of her own volition.

However, as the unicorn stood before her, shifting uncomfortably and rarely looking her into the face, Twilight Sparkle could tell that something was really amiss with her. The things she just said didn't help.

"So... Why again do you want me to stop looking into it?" Twilight asked.

"Not stop, just... take it slow. You're certainly awfully busy with your responsibilities as princess and I don't think we should waste your time with such a minor inconvenience."

The alicorn wasn't convinced. Something was really wrong here. "Sorry, Rarity, but I don't think that a filly having colt parts is 'minor'. Who knows what it could do to her, especially mentally?"

"Oh, don't worry about that. Sweetie arranged herself very well with it." Very well, indeed. "I doubt that it will harm her to have it a bit longer."

"I... see." Twilight was still not convinced. Not only that, but a horrible suspicion crept into her mind. But she brushed away, because there was no way it could be true. And because she really didn't want to think of it. "Well, if you think that it's alright, I guess I can take it easy. But I'm not going to stop looking for a cure."

Rarity chuckled uneasy. "O-Of course not. It's not like I want her to keep these... genitals forever."

A cold shiver went through Twilight. It felt like she heard an unintentional confession. "Right... Well, if that's all, please go aw... I mean, sorry, I can't keep you company longer, I have urgent... princess things to do."

Both mares were glad when they parted, but only one was actually relieved. Twilight's suspicions were... crazy. And there couldn't be any way that they're true. But if they were...

Twilight sighed. It was no use. That was too much for her. So, after a long time, she started to plan a letter for Princess Celestia again...