"This is pretty much your fault, Berry." Derpy stood in front of a bathroom sink with her shirt rolled up. Long practice allowed her to let her milk flow freely enough that it arced into the sink with some force without overwhelming the drain. Unfamiliar observers would probably assume her letdown was out of her control, since she wasn't even milking herself.

She'd considered making more of a mess but eventually decided against it. Really, Derpy had been exceptionally restrained.

The palace tour hadn't been especially exciting. Interesting, sure, and the architecture was nice to look at, if a bit ostentatious, but it was the sort of 'cultural value' excursion that would probably have bored Ruby Pinch and Dinky. They could always go again as a family should the girls express an interest later.

Derpy would have taken the tour anyway, mostly out of a sense of curiosity, but apparently her boobs felt some special significance in wandering around the home of a powerful pony most of the nation held in awe. There'd been an oddly tense sense of anticipation, even though her rack had been generally well behaved.

Her imagination, however, had continuously supplied her with mental images of flooding the pristine halls, or growing until her titanic tits burst out of the palace and took its place, supplying milk to the city and the lowlands around the mountain.

It was fun in a transgressive sort of way to imagine burying Celestia's palace under her tits, but since Derpy didn't want to do actual harm, she should probably leave government buildings intact.

"I'm a terrible enabler," Berry agreed. "Kept it pretty subtle, though, didn't you?"

Derpy wasn't convinced that the Princess saying hello to their group of tourists had been some kind of spontaneous coincidence. Either way, she hadn't wanted to make the moment all about herself. "How often does a pony have a chance to meet Princess Celestia?"

She'd only unleashed enough milk to soak her shirt and leave her bounty dripping copiously off its hem before Berry had firmly requested they be shown to the nearest bathroom.

It made her feel good to control her limitless abundance so precisely, strong and accomplished even when she was worked up more than normal. Of course, cutting loose back at the station had also made her feel powerful.

Occasionally, Derpy liked to imagine what it might be like to grow into a body like hers within hours rather than years, with no chance to acclimatize. To be rendered barely functional by her normal levels of arousal, to be completely helpless before the needs of her amazing breasts.

"Fair enough," Berry nodded. She was leaning against the tiled wall, playing with a coin, letting it wander across her knuckles. Berry had nimble fingers and enjoyed making Derpy think about feeling those fingers on her boobs without saying anything.

Derpy shook her head, then turned her attention back to the mirror so she could gaze into her own cleavage and watch her milk flow. Dreaming about being at the mercy of her constant lust was well and good, but the things Berry could do to her would probably completely fry her brain in that situation, and the other mare had made too much of an effort to learn her way around Derpy's body. She didn't want to be so mindless with pleasure that she couldn't at least appreciate the craft on some level.

More importantly, that sort of thing probably would diminish the emotional component of their lovemaking, which was completely unacceptable. Making Derpy climax was trivially easy, anyone could do it. A lot of things and thoughts as well. She'd never want her mind to be so clouded that she couldn't recognize Berry's hands on her.

"So what now?" Berry sounded amused. "Just gonna stare at your own tits and see how long it takes for someone to check on us?"

Derpy nodded, humming an agreement. She could spend any amount of time contemplating her breasts, time passed quickly that way. It was soothing to just let her milk flow for no real reason. The way it completely failed to make her feel any less full was, as always, deeply reassuring. It was lovely to just take the time to enjoy her keen awareness of her breasts. Their beautiful shape, their weight, how full they felt, and, more abstractly, their eagerness to please, their immense potential for more.

She closed her eyes, allowing herself to sink deeper into the wealth of sensation her breasts provided. Things she unthinkingly tuned out as she went about her life were easily noticed as soon as she stopped to feel and listen. The steady beat of her own heart. The thrum and throb of her production. The slow, ever-present tide of pleasure, always spreading from her nipples, through her bosom to her core, perhaps the reason why her lust could never be fully extinguished. Her milk, flowing through tight, wet passages. A world of experiences for her alone, as unique as her breasts themselves.

Just as her body was strong enough to bear huge breasts, so was her mind adapted to make their extraordinary sensitivity fascinating and rewarding instead of debilitating.

Derpy felt the air in the room change as Berry began to move. Although ordinarily an aspect of pegasus magic, she relied less on her feathers, feeling the shift in air currents most keenly as it brushed across her fur and the exposed skin of her dark, pebbly areola and nipples.

Minute tremors jiggled Derpy's breasts almost imperceptibly as Berry crossed the room with a few quick strides to arrive behind the pegasus. She hoped that her sensitivity would continue to grow as her breasts did. It would be amazing to relax at home and feel her family moving around the house.

"Question," Berry spoke from behind her, wrapping her arms around Derpy's stomach. "If I can make wishes now, how'd you like it best? A request like earlier today, or maybe givin' permission?"

"Oh, I can give myself permission just fine," Derpy responded after thinking for a moment. "Requests, sure. Try giving orders ... might be nice to share the burden of command." She couldn't help but giggle, feeling ridiculous referring to any aspect of her breasts as a burden.

"I'll keep that in mind," Berry murmured before shifting her hands to rest on the sides of Derpy's boobs, gently rubbing them. The earth pony knew to apply a soft touch to avoid snapping Derpy out of her peaceful state of heightened breast awareness.

Derpy wasn't sure how long she'd stood there, simply enjoying Berry's presence, her own body, and the flow of her milk.

Eventually, the door to the bathroom opened from the outside. To Derpy's disappointment, nobody stepped in to gawk at her naked breasts. The voice of a mare addressed them.

"Once you are finished, the Princess would like to see you."

"We'll be out in a minute," Berry called back.

Derpy stopped the flow of her milk. As was often the case, the feeling of fullness was particularly intense for a moment, to remind Derpy that she'd never run empty. She sighed happily before making herself presentable. Without an audience, there was no need to draw out the process.

Berry grinned. "Alright, let's not disappoint the Princess."

The pony waiting to direct them to the Princess looked like a stern sort with her glasses and dark brown hair done up in a bun. She didn't visibly react to seeing Derpy, but turned and strode ahead of them.

The earlier sense of anticipation returned with a vengeance, and Derpy's nipples were already stiff again. Her arousal was already growing, which was unusual. The soothing effect of spending a quiet, relaxing moment with Berry or their daughters normally lasted a little longer than that. Derpy supposed it made some sense, now that they were actually going to see the Princess, part of her clearly didn't just want to show off Equestria's best boobs, but also the fact she was exceptionally good at being horny.

After all, was there anyone else who would be so delighted that her desires were never satisfied, only lessened for a few hours? Who would be so proud to be literally insatiable? But Derpy was doubly proud, both of being built for endless sexual pleasure, and of having the will to be more than that, to maintain her job and her relationships, to enjoy other things in life.

Derpy felt her great glands throb with immense eagerness. She'd just spent however long spilling gallons of milk into a sink, and while that sort of things did appease her breasts reliably, they also often seemed even more responsive to her desires afterwards, as if they wanted to provide additional reassurance that their supply was inexhaustible.

The walk seemed long, and Derpy wasn't sure if that was some kind of power move or if the architecture just shook out that way. Although in fairness, each step of their brisk pace served to maintain the weighty jiggling of her barely restrained breasts, shocks of pleasure pulsing through them, so she probably wasn't keeping track of the distance too precisely.

She felt overwhelmingly productive. It wasn't something she could measure, of course, since the limiting factor of her output were her nipples, but no one looked at an erupting volcano and consoled themselves with the fact that it wasn't going to spew out all of the molten rock available at the world's core.

Of course, Derpy wasn't going to tell anyone outside her family that her breasts could feel full in a threatening way, because it would sound crazy. Sometimes she just needed to completely shatter any preconceptions about what a large set of tits might be capable of and wash the pieces out to sea in an apocalyptic flood of milk. She blamed Berry for raising the specter of the Princess being unimpressed with her.

Derpy wanted to leave the Princess with a lasting memory that would vividly jump to the forefront of her mind whenever she encountered fluids, round shapes and maybe the colors white, grey or blond. She was beginning to feel achingly tight, yet her breasts barely swelled. Preparing a surprise, she supposed.

She took hold of Berry's hand to help her remain centered when she realized that impressing the Princess probably wouldn't be as hard as it would be to surprise Berry. The taller mare had always seemed to take everything about Derpy in stride, being entertained by the way other ponies reacted to her fantastic body.

If Derpy had regular boobs but was really into some obscure hobby, Berry would probably take an interest just to make it more comfortable to maintain their emotional connection and Derpy would probably still ask the taller mare to help her work out. The incredible tits were just an incidental factor of their relationship, although one Berry took full advantage of.

She bit down a moan. Berry taking advantage of her breasts was dangerous thinking right now.

Still, surely, surely meeting the Princess was such a special occasion that her tits could brew up something that would amaze and astound even her unflappable lover?

She missed a step and stumbled when her rack groaned and gurgled in response to the thought. She felt so heavy, a decade's worth of accumulated milk bearing down on her. Berry kept her from falling. Their guide's posture seemed to stiffen further, but she didn't say anything.

"Eager to meet her Highness?" Berry smiled knowingly.

"Y-yeah." Derpy nodded. It was becoming harder to focus, milk kept intruding on her thoughts. Why couldn't Berry just grab her tits and spray down that other pony?

Derpy took a deep breath and tried to focus beyond the urgent throbbing of her nipples and the heat at her core. Should she really be holding back her gift like that? Her boobs weren't really bound by biology, what if that endless vitality went for other outlets and infected nearby mares with fat, gushing tits? It might be better to erupt here and now rather than risk pushing something on other ponies they didn't want.

She shook her head. It had never worked like that. Her mind was just playing tricks on her. Berry didn't want bigger boobs and her body would never betray her by forcing them on the earth pony. Did she smell milk? Derpy reached for her nipples. She hadn't leaked. She could taste her sweet bounty on her tongue.

She had absolutely no idea how they finally arrived at a large room with vaulted ceiling and marble floor. There appeared to be no furniture but a huge bed in the middle and an absurd amount of throw pillows everywhere. A tea cart with snacks was parked by the door Derpy guessed they had just entered through. The bed might actually just be a big mattress on the ground, the sheets looked expensive so it still counted as classy. She didn't see any drains and couldn't stop a demented giggle.

"I think this is the orgy room," Berry commented drily. "No wonder it seemed off the beaten path."

Princess Celestia was very tall. Probably the tallest pony in Equestria. She was elegant and slender, despite being so tall, she was in proportion with herself. She was wearing a white dress which seemed extremely basic, although Derpy doubted it had been cheap. "It hasn't seen regular use for that purpose in a few generations now," the princess responded kindly. "More innocent minds know it as the pillow fight room."

"Good idea," Derpy conceded. There was a reason they had a large shower room in the basement, and it wasn't that Berry had her weight bench down there. It was simply the most practical place to have wild sex without the clean-up being too annoying. Sure, her boobs were always on their best behavior whenever they made love in their shared bed, but sometimes Derpy just needed Berry to absolutely wring her out, and they didn't have servants to clean up after them. She struggled to banish the memories of those times, so she didn't trust herself to explain any of that.

"Hm." The Princess crossed her arms under her modest bust. "Was it thrilling to play your games in my home, my little ponies?"

"Yeah," Derpy blurted out before Berry could come up with a cleverer response.

"I'm glad." The Princess surprised them with her answer. "I'm afraid these current generations of my little ponies are a little staid, at times." She shrugged, speaking fondly. "There are worse things to be, of course. Influencing prevailing attitudes isn't an exact science."

Derpy recognized the home stretch. As long as she kept it together just a little longer, she could make her move. She nodded numbly. Thinking of what was about to happen made it easy to smile.

"So we're here why?" Berry sounded only mildly curious. Derpy knew of course that this was the best case scenario, the whole trip had been planned for Derpy to get her kicks from showing off, but Berry would wait until they were home to be smug about how well it went.

The Princess nodded at Derpy. "I only know you from rumor and reputation, but I would like to hear about your gifts and, if you're agreeable, partake personally."

Derpy stood up straighter and thrust out her chest. "Of c-course." She smiled brightly, feeling like she was about to explode. "B-Berry, do the pitch." She swayed a little, willing her body to be patient.

"Heh, right. She permanently gets a little bigger any time she shares her milk with someone new. Some ponies get a little boost themselves. I guess her milk grants wishes. We've had nobody unhappy with it yet. Some ponies wanted something but got nothin', so maybe her jugs can magically tell if they had a bad reason for it?" Berry shrugged. "Also, Derpy gets incredibly horny thinking about her own tits. That's, uh, that's why she's drooling now."

Derpy nodded. She loved hearing these crazy things about her boobs voiced. She wiped her mouth, then crossed her arms under her boobs and lifted them. "Interested?"

Berry snapped her fingers. "Right, it doesn't do anything to kids except be really healthy. Really healthy. Ain't nobody and nothing her milk isn't good for. Should see our back yard, if our neighbors didn't know us, they'd think I was good with plants or something."

"We had to cut down on having sex in the yard." Derpy giggled again. Their daughters had been very annoyed about all the yard work related chores. She was holding back a great tempest of milk, but at least the land would bloom in the aftermath.

"Have you considered that the magnitude of your bounty might be an indicator of your fertility?"

Derpy moaned. How many ponies could she feed? She could theoretically give milk uninterrupted for twenty-four hours every day. Having more children meant bigger breasts, larger nipples and more output. That way laid unchecked escalation. "F-fun idea, but no. I want to be g-good at raising children, not just -hfff- feeding them. We're good with th-three." She rubbed her thighs together.

"Very well. Still, perhaps you should investigate the possibilities of surrogate motherhood?" The Princess strode over to the bed. Up close it really was too tall to just be a mattress, it was comfortable to sit on its edge for the alicorn. "I'm quite interested in your gifts. If you desire it, I would also be open to satisfying your needs before you leave." She nodded at Berry. "That goes for both of you."

If Berry wasn't okay with having a threesome with Princess Celestia, Derpy would accept it and leave. She'd probably explode somewhere between here and the train, but that would be fun as well. Still, if Celestia thought she was a match for Derpy's libido, Berry would probably just stick around to watch her fail.

The earth pony shrugged. "I'll try anything once." It was the exact thing she'd said whenever Derpy had some suggestion for spicing things up, as though getting an invitation from the Princess herself was just some new twist on having sex with Derpy.

"Alright!" Derpy tore off her shirt and worked herself out of her skirt and underwear. She approached the Princess. Celestia was tall even sitting down but unlike Derpy she could still hunch over quite a bit while seated.

She felt the Princess' lips on her thick nipple. "Watch this, Berry!"

Celestia only had a moment to frown in confusion before the tethers of Derpy's control snapped. Two thick streams of milk erupted from her nipples with tremendous force. The rush of milk stung, force enough to cause discomfort even though her breasts were tuned to provide only pleasure. Derpy climaxed immediately, but she was well past where once would be sufficient.

The Princess recoiled, gagging and coughing. She dropped backwards onto the bed to escape the milk which had already covered her face and drenched her hair. She started moaning, whatever she had swallowed enough to trigger whatever change was to come.

"Hah, damn." Berry sounded terribly amused. She hadn't gotten naked yet, but already had one hand down her pants to warm herself up. Derpy had long since accepted that the manual approach got the best results to get Berry going.

Derpy gasped as she felt her own change coming. Her own growth had always been quite brief, but the felt filled with terrible energy and the pulsing in her boobs told her that this was going to be a big one. She stumbled towards Berry and wrapped her in a hug so the other mare could feel her grow.

Despite years of experience, even Berry couldn't quite keep from flinching when hit with the full blast of Derpy's lactation. She grabbed and spread those twin geysers to stop them from hammering her body. Derpy hardly felt disappointed that she didn't have enough cleavage to engulf Berry's upper body, but something told her that was about to change.

New titflesh bubbled into existence obscenely as her boobs lurched bigger, blasting Derpy's mind with pleasure. Her whole body tingled. She grew more solid in some indefinable way as her body adjusted to more growth than she'd ever had at one time.

Derpy couldn't think, but she felt Berry's hands exploring her body as her hips stretched and grew wider. Her ass also grew fatter and rounder under her lover's hands, full and tight.

"Hm, could park a drink on your hips ... or your ass." Berry whispered, making Derpy squirm.

True to her nature, she was most enticed by the feeling of her breasts enveloping Berry. Their true girth was hard to judge in this position, but it was breathtaking to feel so much of the other pony with her tits alone. With her rack embracing Berry's body, Derpy hugged her and spread her wings to wrap around both of them. Had her wing span increased as well?

In that moment of privacy, she kissed her lover. "Thanks for planning this trip."

Berry smiled. "Gamble paid out better than I expected. Think you did a number on her, though."

With her own growth slowing, Derpy became aware of other moans in the room. She stepped back from Berry, nearly losing her footing as her tits slapped together, sloshing and wobbling. Despite forming a long, tight line of cleavage, each was about two feet across, and even near their base their girth was so great that the skin of her breasts appeared to extend sideways from her rib cage. They dominated her chest, sitting so heavily on her body that they appeared eager to ooze around her torso despite the fact that they clearly maintained an impossibly attractive shape in general.

She wasn't anywhere near big enough to just lay down on top of her tits and sink into their vast softness, but she felt as though she was getting a beautiful glimpse of that future. She was still gushing milk, but her nipples were now roughly the size of Berry's fists, so they no longer strained to withstand the volume of her previous output.

Seeing Princess Celestia was enough to briefly shock Derpy out of her appreciation for her own body. The Princess had grown, Derpy guessed she had to be nearly ten feet tall. She'd burst out of her dress. Her body was not quite buried under a quartet of enormous, heaving tits.

Derpy was pleased to observe that any individual breast was still smaller than her own, and the Princess was not obviously lactating. The royal jugs seemed less firm than Derpy's, judging by the way they deformed as Celestia groped herself. In any case, having two pairs of breasts seemed like an interesting idea to Derpy, although she wouldn't currently be willing to double her current total mass, or divide what she had to make four.

Most surprising however was the enormous dick with which the Princess was titfucking herself as two balls the size of Derpy's head pulsed and churned between Celestia's legs. Her horn was blazing, two additional spectral cocks were thrusting into her horizontal cleavage from each side

"Huh." Berry had moved next to Derpy. "Must have been something subconscious," she declared. "If she'd planned this out she wouldn't be falling just short of sucking her own dick."

Derpy laughed. "Probably, yeah."

The Princess came with a long, sloppy moan, but neither the climax nor a face full of her own cum caused her to falter.

Taking a step forward, Derpy was only kept from falling to her knees by Berry's quick reaction. The pleasure her breasts provided had always increased with their size, but she had never grown this much at once. Yet clearly there had been another change. Derpy stood and reached for her sex. "Touch me, Berry."

"Y'know, you were right," Berry idly commented as she stepped up behind Derpy and reached around to probe her wet snatch. "Getting as much tit as you got at once really does mess a pony up." She made a disapproving noise.

They stopped talking, tenderly exploring Derpy's folds. Her clit was engorged, although what fascinated her were how pronounced her pussy lips had become. Thick and pillowy, Derpy could already picture how amazing they would look with a pair of soaked panties clinging to them. She adjusted her stance, lifted one leg experimentally, and her outer lips were practically fighting for space.

Some other mare might have been concerned about getting aroused just from walking around as her pussy stimulated itself, but Derpy doubted she'd even notice the difference considering how amazing her tits felt once she was in motion. She was already overflowing with sexual energy all day every day. "Do you think you'll like that?" That question was of far greater importance.

Berry's fingers traced Derpy's nethers almost reverently for a while longer before she answered. "Yeah. Feels good. There's so much of you, s'just right if you're plush down there, too."

The Princess was still furiously masturbating.

Derpy huffed, taking a moment to reduce her milk output to a trickle. "I am looking forward to being re-introduced to your tongue, but this was going to be a threesome of some sort and I'm gonna have that dick." The idea seemed ludicrous, but she had a good boob feeling about it. Maybe all of her body was bigger on the inside. "Let's get her all the way onto the bed." The Princess had, after all, fallen back from sitting on the edge.

That did surprise Berry. "Really?" She moved to reposition the Princess, who barely reacted. She probably got a kick out of treating royalty like that. "If you can take that monster, I can stick my arm up your snatch to the shoulder."

"Ugh, it barely sounds hot when you put it like that." Derpy spread her wings and took flight, hovering above the bed. "You gotta help me aim."

The Princess only managed to complain incoherently as Berry liberated her huge rod from the royal cleavage and held it steady. "Man, we have to have a camera on hand when the girls are old enough to hear this story," the earth pony commented.

Derpy slowly lowered herself on the biggest dick she had ever seen. It initially felt like it split her open, but despite the resistance there was no pain. Was her whole body becoming as resilient as her breasts? She lowered herself gently, already bracing herself for a moment of pain, but it never came. She felt herself continuing to stretch around the intruder. She dug her hands under her breasts to place them on her stomach and she could feel it moving inside herself without causing harm.

Derpy laughed. "I really am made only for pleasure! This is amazing." She'd touched down now, straddling the Princess on her knees. She took a breath without difficulty even though she'd taken a cock longer than her arm all the way inside herself. There was also a chance that Celestia had always wished for a giant penis that wouldn't hurt normal sized ponies, but that was the more boring option.

Clearly the Princess also approved as she started bucking her hips.

"N-next step!" Derpy was discovering a new way of feeling full. Not as great as what her boobs could provide, but variety was the spice of life and all that. She dug her hands into her tits. "Berry! You need somewhere to sit so I can eat you out! Give the order!"

Berry's face lit up with recognition. She was as well versed in Derpy's fantasies as Derpy herself. She knelt down next to Derpy and the Princess. Then she hesitated a moment, probably feeling silly. Finally she put her hands on Derpy's right tit. "Alright ladies, grow! And don't hold back on the milk. We want this to be a catastrophe."

Celestia climaxed at that moment. Hot cum flooded Derpy's insides as her breasts started to swell rapidly. She felt her stomach bulge with Celestia's load "Yes! More, Princess!" Derpy came and her milk started gushing again. "More!" She demanded it of the Princess and of her own body.

Derpy got her wish. Maybe the Princess had entered some kind of pleasure cascade, in any case she pumped load after load into the mailmare. Derpy felt herself swelling until she felt as gravid as she'd ever been shortly before Dinky's birth. There should have been some backwash by now, but at this point she could just as well assume that her body somehow turned all that extra cum into more productivity.

It felt incredible to experience her breasts cover more and more of the Princess in front of her. Her tits once again felt full to bursting as they swelled bigger and rounder, spraying huge streams of milk across the room. Derpy stopped being able to keep track of the situation when Berry started experimenting how she was going to get into position. Being fucked by the Princess from below, her breasts being treated roughly by her lover, spraying milk all the while, it was finally enough to overwhelm Derpy momentarily as she climaxed again and again.

She couldn't have lost more than a few minutes. Derpy returned to her senses just in time for Berry to rest her thighs on her shoulders. The earth pony's body was wedged into her cleavage, perfectly position so that Derpy could put her tongue to work.

She took a shuddering breath. "I've dreamt of doing it this way for years." Berry had brought her more pleasure than normal ponies could withstand, so it thrilled Derpy every time she could get Berry off. Getting Derpy to cum was just daily maintenance, business as usual. Pleasuring Berry was special, and she set about exploring the earth pony's sex with her tongue.

"F-fuck, Derpy. You're good." Berry wasn't much for talk during sex.

Derpy lost any sense of time she may have had. She was being fucked by the Princess. Her tits were big enough to support Berry's weight. She was spraying milk, her breasts throbbing, the pleasure of Berry's weight alone supplying regular orgasms. The other mare still had the presence of mind to claw at Derpy's tits just as roughly as she liked it. From below, the felt Celestia's stiff nipples, her huge breasts dwarfed by Derpy's volcanoes. Her thoughts dispersed. Only her pussy, her tits, and the work of her tongue had any meaning as repeated climaxes rocked her. The smell of milk was overpowering.

In fairness, Derpy did feel a little sore afterwards.

The three of them sat on an island in a sea of milk and ruined pillows. The milk level had never overtaken the bed, but clearly the mattress had soaked it up from the bottom. Princess Celestia gazed at the devastation. "We may have gotten a little carried away," the alicorn commented.

"I'm a little conflicted," Derpy mused. "It's fun to see how much chaos I can cause if I just cut loose, but we have good drains in our shower room for a reason. I don't have to stop until I feel like it."

"Our clothing is somewhere in this mess," Berry observed. "I put our wallets into plastic tubs from the kitchen this morning, those will be dry."

Princess Celestia turned to Derpy. "You can't mean that you're still not sated?" Somehow she was more surprised by this than by the fact that they'd spent so much time fucking that Derpy's careless lactation had flooded the room. The alicorn was clearly having to put in an effort to not be distracted by her new body.

Derpy shrugged. "I'm pretty sore," she allowed, knowing that the Princess probably wouldn't understand what a tremendous achievement it was to make Derpy experience even a slightly negative consequence for sex. "So I've had enough dick for ... a while. But otherwise? I could go on. If you wanted to." She fondled her boobs, back to the size she'd gotten after sharing her milk with the Princess.

Berry snorted, well used to the answer. "You literally can't fuck her until she stops being horny, you can only get her to a point where sex is a little lower down on the list of things she wants to get done. That's not on you. And so far no one has been crazy enough to want that for themselves."

"Well, the effect usually lasts a little longer," Derpy stated before sucking in a deep breath through her nose. "Surrounded by this? It's givin' me an itch that I didn't keep going until milk started flowing out the windows."

"Yeah, but please take some pictures and send us copies," Berry added, ably anticipating Derpy's wishes.

"I shall. Now, let us begin our recovery." In a golden flash, she teleported the three of them to a large, private bathroom.

Derpy winced. The bathtub was offensively large even considering the Princess had already been tall previously. There was no shower stall in sight.

Fortunately, Berry had no compunction about wading into the tub and grabbing the shower head above it to spray Derpy down. "You would not believe how bad Derps here is about bodies of water or, uh, containers full of things other than milk," she pre-empted the Princess' questions. "If we sat her down in this tub it'd only be a minute until she forgot why she shouldn't just start gushing until enough water and milk ran over that the tub's mostly milk." She shrugged. "Empty vessels are kinda alright and I can get away with spraying her down because I don't need to be taught how pathetic this is compared to what she could do. Besides, in the shower she can just leak without issue, yeah?"

"It's so amazing," Derpy couldn't help exclaiming. "Having you explain that stuff so matter of fact is really doing it for me, so maybe don't keep going."

"Heh, alright," Berry conceded. "You did real good today. Even caught me off guard."

Derpy couldn't help but preen, delighted by the other mare's approval.

"I suppose it's good fortune that you enjoy every aspect of your powers." Celestia looked at herself in a huge mirror. "This reminds me of a delightfully salacious story about myself I had the pleasure of reading about a century ago. I hadn't been aware of how much it stuck with me, to be embarrassingly honest!"

The Princess turned to face them. "I'm afraid you'll have to swear secrecy regarding these changes. I will have to disguise them and grow into them gradually over the next year or two." She smiled. "Perhaps we can repeat this once I've grown used to these changes and can apply a little more skill and a little less instinct to the encounter."

Derpy smiled, delighted. "Oh, that won't be a problem at all."

After all, she still needed to sound out the Princess on what she might think about tits the size of mountains. Many potential problems would probably be easier to solve with such a powerful pony at least implicitly approving. Maybe she could set her mages and sages to look for a parallel dimension no one was using anymore!

Author's Note

I don't feel very confident about writing Celestia in the context of smut.