Portalbelt XXX

by SquiggelSquirrel

Rating: mature
Tags: Twilight Sparkle, My Little Pony: Friendship is Magic, Portal, Porn, Rarity, Sex
Length: 8984

Rarity gets locked into a portal sex belt

Rarity wears an Aperture Science Portal Belt XXX — like a chastity belt, but with glory-hole portals over both orifices. Twilight has the controls, and the keys. There's a portal mask for oral, and Twilight has plans…

Contains some futa characters, including Twilight.

Consensual but not entirely safe or sane bondage.

Thanks to Bronyb3n for commissioning me to write this.

Published 2018-02-11 10:40:06 UTC
Last updated 2018-02-25 23:25:14 UTC

Why is it glowing?

Twilight had that look in her eyes — the look that left Rarity nervexcited, terroraroused, hornyscared — turned on, yet decidedly apprehensive. It was the look that said Twilight was planning another of “those” experiments, the ones Rarity suspected that Twilight secretly enjoyed the most, the ones for which Twilight increasingly seemed to favour Rarity as a “test subject”.

That wasn't to say Twilight had become less interested in exploring the magic of sexuality with her friends — of whom she now had many in Ponyville — but Rarity was one of the five Twilight was closest to, and most likely to share new experiences with.

Like the time she'd nervously revealed to them all that she had "male" sex organs, along with her marehood. Things had progressed much more swiftly after that. Learning that she wasn't alone in this, that Applejack was also a “pony of both parts”, had been a comfort that really brought Twilight out of her shell.

No, Rarity suspected this bias was more an alignment of taste. Twilight, it seemed, rather enjoyed tying somepony up, or strapping them down, or locking them in, as the case may be. She enjoyed designing and demonstrating devious devices to dominate and degrade. With such creativity for contriving sexual torture, Rarity at least half-suspected Twilight would one day invent and entirely new fetish, if she hadn't already.

But Twilight was a good pony, who would never intentionally harm anyone (without good cause). She needed a suitable submissive subject, somepony who enjoyed being reduced to a mere sexual plaything and thoroughly used, both by Twilight and by anypony else who joined the “experiment”.

Rarity gave a small embarrassed chuckle as she contemplated her train of thought, and how she couldn't deny her eagerness to be Twilight's favoured test subject.

“Hi Rarity!” said Twilight, radiating forced casualness. She had entered the boutique late on Friday afternoon, when Rarity was just preparing to pack up. “Are… you busy this evening?”

…

An hour later, the boutique was closed, Rarity had cleaned herself — outside and inside — in preparation, and Twilight had set up some… apparatus, on the table in Rarity's living room. The blinds were pulled shut.

“So, uh…” Rarity began, looking around the room, “will it be just the two of us tonight?”

Twilight smiled. “Oh, well, I was planning to involve some other participants, if that's alright. But they won't be here, exactly.”

Rarity frowned in slight puzzlement at this, but then she rather enjoyed being surprised by Twilight's creativity, so she only nodded and murmured assent.

Twilight coughed, and her face shifted to a more business-like expression. “Now then. There will be no safeword for this experiment, instead you need only leave the couch to end things early.” She gestured to the furniture in question. “Of course you will not be restrained from leaving in any way. Is that acceptable?”

“Yes darling,” Rarity nodded, making her way over to the couch. No safeword, she thought, most likely meant that her mouth would otherwise be occupied. That was good to know.

“Before we begin,” continued Twilight, “I need you to put this on.” She levitated a package from her saddlebags. “I'll help you ensure that it's in place properly, but it will be easier if you take the lead.

Opening the package, Rarity glanced at the attached documents, the words “Portal Belt” immediately conjuring up some ideas. The device indeed resembled a chastity belt of sorts, with moulded cups for her teats and a pair of flat-ish boxes positioned to cover her private areas. The rear strap included a dock ring, and the boxes were emblazoned with circular logos.

Ah yes. What was the name of that company again? Atomicky scientists? Something beginning with “A”. Twilight had been talking about them quite a bit lately. Quite an… esoteric lot, from the sounds of it.

The belt seemed quite well made. The straps were adjustable, the entire inside lined with a soft rubbery grip. Twilight gripped Rarity's tail and spread her buttcheeks while securing the harness over her hips, ensuring that the whole contraption wouldn't budge even slightly.

Once both ponies were satisfied that the belt was in place, Rarity climbed onto the couch. She couldn't quite sit normally with her dock lifted by the belt, so instead she leaned back to a more reclined position, legs spread apart.

Twilight lifted some manner of control panel from the table, pressing buttons with tiny clicking noises. The logos began to glow with green light.

“So, ah…” Rarity asked, playing innocent for fun. “What exactly is a ‘Portalbelt Thirty’? … and why is it glowing?”

Focussed on the device between her legs, Rarity failed to notice the other device that Twilight had lifted — another small box, with a seal shaped to fit over a pony's mouth, and three straps, one ending in a ring. In a single smooth motion, Twilight pressed the mask to Rarity's face, clipping the ring over her horn and buckling the straps around behind her head. The mask fit tightly in place, forcing Rarity's jaw open slightly and squashing her muzzle.

Feigning annoyance, Rarity twisted around, closing her legs together defensively and gesturing the mask. “Mmpfh!” she intoned in Twilight's direction. “Mm-mmfh.”

Twilight only grinned, biting her lower lip and perching herself on a futon in a relaxed, spread-legs position. Her member stood proud, bulging from its sheath, but for now Twilight focussed more on Rarity, and the control panel.

A button pressed, and Rarity felt the gentle tug of suction on her nipples. The moulded cups gently squeezed, suction rising and falling in a mechanical massage.

Another button pressed, and the device around Rarity's nethers emitted a mechanical *bleep*. She felt a brief prickle of static around the edges of her already aroused pussy, followed by the flow of cool air, as if the cover had been removed and exposed her. Twisting back, she spread her legs again to see what was happening, vocalising her muffled puzzlement. The glow had changed from green to orange, but from the outside there was no other visible change.

Then something pressed up against her folds. Something warm, hard, and fleshy. Rarity offered a tiny “meep!” of surprise, as the anonymous cock-head worked its way in between her lips.

…

Above the Sofas and Quills store, Davenport contemplated the pale grey dome resting on his bed. Twilight Sparkle had left it with him earlier today, explaining her plans and inviting him to participate. She'd sent him the go-ahead signal just under an hour ago, and he'd made himself ready and waiting. As strange as this device was, if it functioned as Twilight had described…

The dome bleeped at him. The one flat panel bearing the circular logo seemed to ignite with a boldly blue flame, and then the flames themselves swirled outward into a ring around the edges, condensing down into a rim of glowing magic, within which there was a hole, as if the surface had burned away to reveal the inside of the dome.

Inside, though, was not machinery but a quivering, dripping vagina. From the colour, Davenport could make a fair guess as to the owner. He smiled, testing the edge of the portal with his hoof. If he was going to be burned or shocked, better his hoof than his balls. The magic was hurtless to the touch, however. Satisfied of his own saftey, he brought his quite ready stallionhood to bear. Slowly and gently, he rubbed the head between the lips, lining up with the opening. He felt it twitch, the clitoris winking in anticipation.

Lowering himself onto all fours on the bed, closing his eyes and picturing Rarity's face. Then he began to thrust, burying his shaft deeply into her love tunnel, intent on making the fullest use…

…

Rarity gasped, and began to rock back and forth on the couch as the unidentified stallion drove his way deeply into her well-lubricated folds, immediately stretching her out and filling her up. With the portal affixed directly over hew marehood, her movements did nothing to mitigate the eager thrusting, and she could only do her best to relax into it, riding out the rough usage.

Her moans were interrupted when, with another bleep, a portal opened in front of her mouth.

Brow furrowing in trepidation, she turned her eyes to Twilight, who was grinning hungrily while lifting a grey cylindrical device into the air over her own penis. A blue glow from one end of the device illuminated Twilight's front. A few clicks, and Rarity felt small but hard metal rods push in between her parted teeth, forcing her jaw open further. Not wish to suffer more, Rarity relaxed as much as she could, and allowed the rods to pry her mouth open to its fullest. She continued to moan from the stuffing her pussy was receiving, only now she could hear the moans like an echo from Twilight's direction.

Twilight brought the tube down onto the end of her cock, and Rarity felt the member pass her lips and enter her mouth. Rarity stroked the head with her tongue, tasting the salty pre-cum. In slow motions, Twilight began to slide the tube up and down. With each stroke, Twilight's penis pushed to the back of Rarity's mouth, sliding over her tongue.

Rarity slumped back against the cushion, continuing to buck her hips helplessly around the shaft filling her cunt, and allowed her head to fall back so as to more easily accommodate Twilight's member. Twilight responded by thrusting deeper, penetrating Rarity's throat until she couldn't breathe, making Rarity gasp when Twilight pulled back, only to thrust in again before Rarity had a chance to recover.

Rarity was not a stranger to group sex, but she had never been so helplessly out of control, so thoroughly dominated. No matter how she twisted or turned, the belt and mask gripped her face and nethers, the cocks continuing to thrust into her mercilessly from both ends. Her eyes watered as her throat became Twilight's cocksleeve. Her vagina spasmed and her body twitched as orgasmic pleasure gushed from her marehood, and her lungs fought for air. Whoever was using her pussy was no quick finish, Rarity was well on her way to a second orgasm but he seemed no closer to finishing.

Some part of the device spurted thick goo over her anus, a nozzle pressing in to pump lube into her rear hole. She never heard the soft *bleep* over her own coughing and gulping, and the rushing in her ears, but she new what was happening next…

…

Big Macintosh was in his room, waiting to see if this box Miss Twilight had left with him would indeed function as described. When it bleeped at him and one face vanished in a swirl of blue light, he nodded and brought his head down for a closer look.

If that wasn't Miss Rarity's asshole, glistening with lube, shuddering as the surrounding muscles spasmed, then he was a filly. The thick stallion-meat swelling between his legs suggested that wasn't the case.

Satisfied that Miss Twilight's magic was indeed working like she said, Mac placed his hooves on the side of the box, gripping it firmly on the edge of his bed. He planted his hindlegs apart for stability, and raised his member to the proffered hole. He rubbed a little extra lube onto his shaft — a bigger cock meant more lube was well-advised — and leaned forward to gradually but firmly push his way in.

…

Rarity's eyes were rolling back. Her legs were attempting to vice-grip thin air, and were completely crossed as a result. Her backside was completely impaled, stuffed to her utter limit with big, thrusting cock, and Twilight continued to use her throat as a fleshlight. Orgasms wracked her body as her back arched, forelegs pushing her chest upward as though changing the angle of her body would help accommodate the dicks stuffing her.

In her vagina, the thrusting stopped, the stallion hilting his shaft, flare swelling up within her as cum pumped into her, only increasing the pressure. Seeing this, Twilight stopped holding back and picked up the speed. In moments, she was likewise pumping seed into the helpless Rarity, in this case straight into the mare's stomach.

Rarity thrashed helplessly as her lungs burned for air, dizzy asphyxiation threatening to overwhelm her, when Twilight pulled out into her mouth, cock still pumping seed faster than Rarity could swallow. She choked for air around the mouthful of cum, goo filling her nostrils and bubbling out of her nose.

Rarity collapsed back onto the couch. Twilight's cock was withdrawn and the bars holding her jaw shut had gone, but all she could do was gasp and moan as her belly bulged from the mighty cock filling her ass, continuing to thrust even after her pussy had been left empty of cock, but still dribbling excess cum.

When the stallion pumping her rectum finally climaxed, thrusting in deeper than Rarity had believed she could take, all she could do was wail helplessly and continually until the shaft was withdrawn.

With a final set of bleeps, the various devices returned to their neutral green glow, the portals closed as two satisfied stallions went to clean themselves off.

Twilight, meanwhile, unstrapped Rarity's mask, and joined her on the couch, kneeling beside her head.

“Clean me off?” Twilight said, slapping her slimy, half-erect cock onto Rarity's face. As far as Rarity was concerned, it didn't sound like a suggestion. Embracing her submissive role, Rarity opened her mouth and got to work cleaning. Twilight levitated over a bottle of water, with a straw. She dribbled it over her own cock, helping to wash off the other fluids into Rarity's mouth. When Twilight was satisfied with the cleaning, she slid off the couch and gave the bottle over to Rarity, who gratefully gulped the water down as Twilight took a damp cloth to wipe down Rarity's messy face.

Rarity was well aware that her hair and makeup were both beyond messy right now, but she could put up with post-coital messiness, at least until she had the strength to get up and deal with it properly.

“Are you akay?” asked Twilight gently.

Rarity panted, and nodded. “Yes, okay…”

“Great!” exclaimed Twilight, bouncing up and lifting a checkbox from the table. “It looks like everything is functioning well, and I've gathered plenty of data from phase one!”

Rarity's expression froze. Then her eyes slowly widened. “Phase… one, darling?”

Twilight beamed. “Oh yes. I mean, as long as you're okay with it. I'll give you some time to recover, and then we can try out the cleaning protocols, those will be essential if you're going to wear the belt for more than an hour or so, especially in this state… oh I have so many ideas, and a planned schedule of course.”

Rarity stared at Twilight. “More than…” she repeated weakly.

“Oh!” exclaimed Twilight. “We can go back to regular safewords, now. I mean, I can't expect you to stay on the couch all weekend.”

“All…” Rarity squirmed “weekend!?”

“Mm-hm,” affirmed Twilight. “I mean, if you don't mind helping me test out prolonged belt use. Just a couple of days should be enough for the tests I want to run, assuming of course I give you time to recover in between.”

Rarity lay back on the couch, eyes gazing unfocused through her ceiling. It wasn't as though she'd had any real plans for this weekend, but she had a feeling that two more days of Twilight's “testing” would thoroughly wreck her.

Well she couldn't say “no” to that now, could she?

Glory

The next few tests gave Rarity some chance to rest. First, Twilight wanted to document how easily Rarity's nethers could be cleaned without removing the belt, and so Rarity endured the disconcerting sensation of Twilight applying a shower-jet and flannel through the portals, scrubbing down her aching vulva and anus — a process that was drawn out by the excess semen oozing and lube out of both holes. Eventually, the flow ceased and Twilight was able to finish the job to her own satisfaction. Having recovered her breath and the strength in her legs in the meantime, Rarity was then able to put the shower to work on herself, smoothing out her messed-up mane and soothing her tired muscles.

Twilight stood outside the shower, taking notes but also displaying obvious interest in watching Rarity work the soap suds all over her body. Around halfway through, Twilight stepped out of the room to fetch some additional device, which she then proceeded to set up over the bowl of Rarity's toilet…

Having established that Rarity could, indeed, use the toilet via the portals — an experience made only worse by having Twilight watch and take notes — and having cleaned up after, the two proceeded to Rarity's kitchen, where Twilight insisted on attempting to spoon-feed Rarity through the portal mask.

The attempt proved somewhat successful once the central strap had been removed — before that the mask held her jaw too tightly and prevented chewing. Twilight scribbled down some more notes, muttering something about a redesign. After that, the mask was removed and Rarity allowed to finish her meal in peace. Twilight explained that she had further arrangements to put in place, and that she would return the next day at 11. With that, she departed, leaving Rarity alone with the belt secured in place and the controls explained, should she need to use the bathroom again in the meantime.

It wasn't the first time she'd had to sleep wearing a chastity belt. At least this one was more comfortable than the last.

…

True to her word, Twilight returned the next morning at 11am sharp, saddlebags bulging with new equipment.

“So then dear,” asked Rarity once they were both inside, “more testing?” She smiled nervously.

“That's right!” Twilight smiled. “I'd like to set up in your bedroom, if that's okay.”

“Of course, darling.”

Rarity followed, and watched Twilight unfold a set of panels which attached to the headboard of Rarity's belt. There was a pair of dials, both reading zero, both with space for double-digits. There was a flat, grey-white board in the middle. There were shackles on either side. Those at least, Rarity recognised the function of.

“Alright, Rarity. For this test I'd like you to lie on your front with your forehooves secured here” — she gestured the shackles around the headboard — “and I'll secure your hindhooves at this end.” She lifted another pair of shackles from her bags — Celestia only knew how she fit so much in there. With more portals, maybe.

Rarity climbed into place on the bed as directed, positioning her head in front of the central board, and spreading her legs so that she could be secured into place. A quiver of anticipation ran through her as the last lock clicked into place.

“Ahem.” Twilight raised a pointer to indicate the dials. “Today we'll be testing the portals' interaction with my orgasm detectors. These 'cum counters'” — she gestured the dials on the left and right — “will track the number of orgasms achieved. The left panel will count orgasms you administer orally.” She lifted a simple collar with a small pink heart on it into place around Rarity's neck. “You can open the portal on this panel by directing a small amount of magic here,” she gestured a small orb at the top of the panel, “and it will gently repel any intruding material before closing automatically after it registers an orgasm.

“The right dial will track any orgasms other ponies experience through the belt, and any that other ponies give you. Those portals will operate automatically, once the experiment begins. The other ends are set up in Ponyville spa — Saturday mornings are always busy, so there should be no shortage of patrons.

“To release the locks and end the experiment, there needs to be a total of at least four orgasms on the dials, with more on the left than the right. Do you have any questions before the experiment begins?”

“Uh…” Rarity shook her head, processing the implications of this set-up. “N-no, that all makes sense…”

“Great!” exclaimed Twilight, pushing a button and causing the machine to bleep.

Rarity froze up, caught unprepared by the sudden commencement. Automated nozzles once again deluged her butthole in lube, pumping a generous dose directly into her rectum before withdrawing. She tensed in surprise, tugging against the restraints holding her firmly in place, and barely regained her composure enough to relax for the first stallion to enter her quivering pussy.

This stallion seemed willing to take things slowly — fortunately for Rarity, as he was by no means small. Thinking fast, Rarity realise she had already given a head-start to the opposition in this challenge, and directed her magic to the controls, preparing to suck her first cock of the day to climax as quickly as possible.

When the portal opened, however, what greeted her was not a penis, but a familiar-looking yellow pussy, spread to reveal the pastel-pink insides. The sight gave Rarity paused — surely this marehood belonged to Fluttershy, who had always been so hesitant about anything sexual…

Another penis rammed against Rarity's butthole, stretching her ponut around the well-lubricated glans. Coupled with another, deeper, thrust into her vagina, it reminded Rarity that she hardly had time to hesitate. She dove forwards, pressing her muzzle into the hot wet folds in front of her and closing her lips around Fluttershy's clit, causing the pussy to twitch. Rarity was more used to providing fellation than cunnilingus, but that certainly did not make her inpet.

She moaned as both her rear holes were filled, pushing the vibrations from her throat onto her lips. She rubbed her face up and down against Fluttershy's entrance, tongue working her friend's love button as she alternated licking and sucking, building up a steady rhythm to outpace the double penetration she was receiving in her rear.

Rarity could feel the tension starting to build within her loins, promising her the first orgasm of the day. Remembering that her own orgasms would be counted against her, Rarity fought to keep her mare-parts under control, breathing steadily while working Fluttershy's cunny as best she could.

The dials chimed as the cock in her ass reached a climax, and began pumping its seed into her. From Fluttershy's quivering, she could tell the other mare was close, but if Rarity had to satisfy at least another two mares after this, her tongue was going to get tired fast.

The stallion in her pussy was still going slow, but Rarity was struggling to keep calm under the deep, filling strokes. If she and the stallion both came, that would be three points against her… she silently willed Fluttershy to finish faster, trying to decide if it was worth switching tack to try and bring her to a climax sooner, or if that would only waste time. She tried running her tongue in circle's around the other mare's clit instead of sucking, and was rewarded by Fluttershy's folds clamping down on her muzzle, fluids spraying onto her face and into her open mouth.

The dial chimed, as Fluttershy continued to quiver. Meanwhile, the stallion in Rarity's ass withdrew, gently tugging her insides as he went. The stallion in her cunt, though, was picking up the pace, and Rarity knew her own orgasm was becoming unavoidable.

She pulled away from Fluttershy, hoping to quickly move on to the next pony. Sure enough, the portal closed off. Rarity knew she needed to send a pulse of magic up to the controls, but focussing was becoming hard as the tension of her rising climax threatened to overwhelm her. She barely managed to focus through the tension, to activate the portal a second time, before the dial chimed to count her own peaking orgasm.

He cunt spasmed as pleasure pulsed through her, against her protests. As she clamped down on the stallion's cock, he too reached his climax. The dials chimed again as his cum spurted into her. She was still shuddering when another penis, this one dark brown and mottled, emerged from the portal in front of her. Not wanting to fall behind, she quickly threw herself onto it, sucking and licking it fervently even as she rode out the spasms that shook her body.

Before the stallion in her cunny had a chance to withdraw, another cock drove deep into her slime-coated anus. Her limbs continued to tense against her restraints as her hips bucked helplessly against the twin shafts. She drove the cock in front of her into her throat with desperate abandon, its entrance lubricated by a mix of her saliva and Fluttershy's juices. Whichever stallion she was swallowing on responded with thrusts of his own, matching Rarity's speed. She had no idea who this belonged to, or if they had even met, but at this point she hardly cared. Her eyes watered as she forced his cock deep into her tight throat, rushing to finish him as quickly as possible.

The stallion who had filled her vagina withdrew, and she enjoyed only a brief respite before the portal over her pussy switched to a different patron. Almost immediately, a tongue pushed into her folds, eagerly scooping out the residual cum. Mare or stallion, she had no idea, but this anonymous pony was clearly eager to taste Rarity's sticky, cum-filled cunt.

The shaft in her anus was not especially thick, but it was long and Rarity felt it ram deep into her insides. With the other shaft sunk deep into her throat, the phrase “spit-roast” had never felt more apt.

Whichever pony had chosen to lick out Rarity's cunt, was now moving onto her clit, seemingly with every intent of making the bound mare cum once more. Though the tongue work wasn't fast, Rarity realised that she was dealing with somepony more skillful then herself, as she felt the first shivers of pleasure run through her sooner than she had anticipated.

Salty goo filled her mouth as the dial chimed once more. She slipped down off the shaft, swallowing some of the seed but allowing much of it to spurt over her face when the cock popped out of her mouth, the still-erect shaft slapping heavily against her brow. She lay panting, still doing her best to ride out the combined thrusting and licking assailing her rear, as she waited for this stallion to withdraw so that she could begin sucking the next.

Trying to gather her thoughts, she turned her gaze to the dials. Two points on the left and three on the right meant she needed at least three more to win… She wondered if she would ever catch up, and how long Twilight would allow this to continue if she could not.

Before she could dwell on that for long, the stallion in front of her had withdrawn, and she was facing a blank panel again. She focused her magic and opened the portal once more, preparing to deliver her third bout of oral. She still had her safeword at least, loath as she was to use it, but if Twilight believed Rarity could do this, then she at least intended to give it her best effort.

Another stallion pushed his shaft through the portal — this one a creamy yellow, with a reddish-brown head. She greedily wrapped her lips around it, running her tongue around the tip and purring into it. Somepony was sucking on her clit and she was powerless to prevent the fresh orgasm welling up inside her. She felt a mixture of relief and emptiness as the cock in her ass withdrew — she wasn't sure if he'd cum inside or not…

This cock resisted her efforts to deep-throat, pulling back when she pushed forward, so she switched to heavy tongue action instead, twisting her head from side-to-side as she swirled her tongue around his glans. She forced herself to continue this steady rhythm even as her second orgasm began to wash through her, somepony lapping up every drop of fluid squeezed from her pussy.

Thick, salty goo flooded her mouth and this time she gulped it all down without even thinking. The shaft withdrew, and she summoned another. Somepony was sticking a tongue into her butthole. Another cock was stretching her cunt and her belly was being rammed into the bed.

Before long, things started to blur. How many stallions had she fellated? She didn't stop to look at them now, just sucking and thrusting as fast as her throat could take, the taste of cum permanently filling her mouth. Her face was covered in goo. Her ass and pussy both ached, but another orgasm assailed her — how many was that, now? She was almost certain she was gaining ground, that she must be close to the orgasm that would tip the balance in her favour, releasing the locks and finally allowing her to rest, but her eyes were blurred and she didn't have time to stop and look properly.

Another stallion emptied his load down her throat, before withdrawing. She summoned the next portal to be greeted by another marehood — this one already oozing cum. Without hesitation, she dove forward to begin pleasuring the other mare, fully ready to suck cum from a stranger's pussy.

At the same time, a mouth closed on her own fold, tongue swirling around her clit. She sucked, and somepony sucked her. She ran a tongue over the strangers folds, and somepony ran a tongue over hers…

She hesitated. The licking stopped. Another penis was slowly working its way into her ass, but Rarity… she stared at the pale grey pussy staring back at her, twitching when she twitched, her own pussy.

Confused, she glanced at the score. Both dials displayed a twelve — if she could pleasure one more pony, she would win… but if she had another orgasm, that would count against her — was winning impossible?

Twilight had noticed Rarity's confusion. “If you make yourself cum, it will only count on the left dial.”

Rarity nodded, and immediately dove back in, relaxing into the autocunnilingus. Just one more… she just needed one more orgasm to win. She sucked and swirled, letting her own pussy telling her exactly how to deliver the fastest pleasure. Just a little more… she was so close.

The dial chimed, but not from her. Another load of semen filled her intestines, another stallion finding pleasure in her asshole. She pushed forward. Two more — she could manage two more.

The stallion withdrew. Shortly after, another entered. Rarity quivered, pushing herself right up to the edge. Another cock slid into her ass, but the dial chimed as Rarity shook from her self-administered orgasm, drinking cum and marecum straight from her own cunt. One more — it was a race against this stallion, who only had the slightest head-start.

Twilight moaned. The sound surprised Rarity, but she didn't let it distract her. A cloth wiped Rarity's face, wiping the goo clear from her eye so she could see more clearly. There beside her, Twilight had set up a chair, and was working a portal-fleshlight down her own shaft, taking Rarity's ass herself. Rarity shot a dirty look in Twilight's direction, but didn't let up from sucking on her own cunt.

Twilight grinned impishly. “Hah… sorry Rare, couldn't resist…” She rubbed the toy up and down her shaft, impaling Rarity's asshole, cum oozing out with each thrust. She lifted a vibrator to her own pussy, part-hidden beneath her ballsack, to order to doubly pleasure herself. Rarity recognised Twilight's moans and knew how close her friend was.

She redoubled her efforts. Her mouth ached; Her tongue threatened to cramp up. All the muscles in her rump were screaming at her to take a break, but Rarity knew she needed to finish before Twilight if she didn't want this to drag on. Through sheer willpower, she drove herself onward to a shattering, all-consuming orgasm. Her ass gripped Twilight's cock so tight, Twilight couldn't pull her own median ring out. Her cunt squeezed until her muscles burned. Her body shook and she threw back her head with a howl of torturous ecstacy.

When she finally came down from her peak, the locks were gone, and she curled up tight. Twilight had cum from the spasms of Rarity's climax, coupled with her own masturbation. Rarity hadn't really noticed. She lay quivering, her body continuing to spasm even as the last dregs of strength left her. Twilight set about cleaning Rarity's ass and pussy, this time using her own mouth to do so, gently and slowly lapping all the excess fluid away. When she finished cleaning through the portals, Twilight climbed up onto the bed and began licking clean Rarity's face. The two said nothing, but Rarity slipped her legs around Twilight and held her close, so Twilight stayed beside her and returned the embrace.

The two stayed motionless together for over an hour before Rarity broke away, rolling onto her back.

“Darling…” she breathed… “could you perhaps… help me to the bathtub? I think I need a long, hot, soak.”

…

Across town in Ponyville spa, Pinkie Pie licked her lips and patted her belly. She'd guessed correctly — cream-filled Rarity tasted good.

Two-for-one

Twilight stayed with Rarity the rest of the afternoon. She claimed it was for observation purposes, and she continued to take notes, but Rarity suspected that her friend (mistress? domme?) was worried about her. Rarity knew Twilight always ended up feeling guilty after their more extreme sessions, the Element Bearer of Friendship couldn't let her dominant side out without worrying she'd gone too far.

Of course, if Rarity did or said anything to call attention to this, it would only make Twilight feel more guilty for spoiling Rarity's enjoyment of the submissive role. The discussion would have to wait until after the experiment was over, and in the meantime all Rarity could really do for her friend/mistress/etc. was to keep smiling and enjoying the attention. Not that Rarity minded a little pampering, especially (her loins quivered at the thought) if Twilight still had another day of this experiment planned.

And so most of the afternoon became a visit to the spa. Rarity was able to recover and unwind with a soak, a massage, and some time in the sauna. Twilight was able to take even more notes on the belt's resistance to water and heat, and they were also able to thank the Spa twins for their help in setting up the morning's activities. Rarity knew the pair could be trusted for their expertise and discretion in selecting participants.

Both mares blushed and stuttered though, failing to meet Rarity's eye. From their response, Rarity suspected that not one but both of them had themselves chosen to take advantage of the opportunity — not that Rarity minded. She knew Lotus had both mare and stallion parts — though Aloe, she recalled, was “all mare”. She'd certainly eaten out at least one pink pussy this morning — though she had to admit, the uncertainty was a little embarrassing. Twilight collected a list of participants, of course, for scientific completeness, but Rarity felt it would be most unsporting to ask for a copy.

By the time evening rolled around, Twilight was looking jittery. They returned to the boutique, and had barely stepped inside before her doubts rose to the surface.

“Are you sure you're okay? You've been wearing the belt for over twenty-four hours now, and you've been through a lot of strenuous activity. I know we planned the whole weekend, but we can cancel early if you're not feeling up to it.”

Truth be told, Rarity had been having a few doubts herself. If the last two sessions were anything to go by, whatever Twilight had planned for tomorrow might be more than she could handle.

“Well…” Rarity hesitated. She didn't exactly want to end this early, either, “why don't we discuss what you had planned for tomorrow, darling? I know we both normally prefer to keep it a surprise, but…”

“Okay.” Twilight nodded.

She stayed for dinner, and they discussed her plans for the day ahead. Rarity was relieved to learn that the planned activity was not as physically strenuous, and she marvelled at the other mare's creativity. Once again, Twilight left the controls with Rarity, who turned in early and slept with the belt on, fatigue from the day carrying her to sleep swiftly…

…

Mid-morning the next day, many ponies greeted the two of them, as they walked sedately through the streets of Ponyville. The enthusiasm of some other ponies may have been in part due to their activities the previous morning — Rarity looked forward to at least a week of embarrassed speculation every time somepony acted friendly toward her — but may also have been due, in part, to the elaborate dresses, manestyles, and makeup both wore. The inhabitants of Ponyville were not used to ponies getting “fancied up” with any frequency.

Their enthusiasm was almost certainly not, however, due to the main cause of the girl's embarrassment. After all, only the two of them knew of the “belts” they were both now wearing, along with the ring keeping Twilight's penis quite erect and throbbing, nestled snugly inside Rarity's cunt. To keep it that way, both ponies kept their pace slow and gentle, as they made their way through the busy crowds, across town, towards Sweet Apple Acres.

Every so often, Rarity would clench up, giving Twilight a playful squeeze.

It was a nice feeling, having somepony just there, inside her, not pounding her silly, barely moving back and forth with each step, occasionally twitching against her walls.

…

By the time they reached the barn, Rarity was quite worked up and ready for the next step. Judging from Twilight's expression, the feeling was mutual. Twilight knocked three times on the door, which creaked open to reveal Applejack's eye, peeking out at them through the gap. Seeing who it was, Applejack opened the door wider and beckoned them both inside.

Once the two of them were inside, Applejack shut and barred the door behind them. Almost immediately, Twilight dropped into a seated position on a nearby hay bale, back against one of the wooden pillars.

“Fuuuck!” she exclaimed loudly.

“Language, darling.” Rarity giggled and pressed a hoof to her belly, pushing hard enough to feel the bulge of Twilight's shaft inside her, massaging herself deeply in the hope that some sensation would transfer through to Twilight's dick. Apparently, some of it did, as Twilight tilted her head back and moaned.

“Yeah, Twi!” Rainbow Dash exclaimed, dropping from the rafters to land between them. “Why would a pretty pony like you use dirty words like that?”

Twilight shot Rainbow Dash a dirty look, but while at the same time hitching up her own skirts to gain access to the device underneath.

“You, uh, did get yourselves awful prettied up for coming here,” Applejack commented.

Rarity grinned, and leaned in towards her. “Well, we know how much you like mares in pretty dresses, darling.” She reached up and nipped gently at Applejack's ear while the farmpony blushed.

“Ugh,” Twilight granted, having unfastened her belt. Slowly, she lifted the panel from her crotch, the portal within slowly divulging her slickened shaft with a soft wet sound. Rarity shuddered as the throbbing phallus was slowly extracted from her. All eyes were on Twilight's penis, though. No pony moved or spoke, so when the portal reached the end of her dick, the wet plop of her glans pulling free of Rarity's dripping snatch filled the air.

Twilight turned the panel outwards, so that the other girls could all see Rarity's still gaping vagina. Applejack whistled.

“That,” Applejack said, “is some nice gizmo you've built there, Twi.”

“Really,” Rarity faux-pouted, “the 'gizmo' is nice, huh?”

“Well, I can use that to pump your pretty pussy, right?”

Twilight had lifted a grey cylinder from her saddlebags, and now she transferred the portal from the belt to the fleshlight, which she passed over to Applejack. She grinned. “I was thinking you could pump her pussy while you sit on her face — double the pleasure, right?”

“And we just watch?” interrupted Rainbow Dash.

“Actually, Rainbow, I was hoping you could fuck me with my own penis.” Twilight lifted a third belt from her bags, and offered it to Rainbow Dash.

“Oh, I am all over that.” Rainbow grabbed the belt and began slipping it into place around her hips.

Lifting her skirts, Rarity trotted over to just beyond Twilight, where somepony had set up blankets over piles of straw — a padded floor perfect for rutting. Applejack followed behind, just close enough for Rarity to flick the farmer's nose with her tail.

Rainbow finished securing the belt, and Twilight activated the portals before slipping her own belt back down over her shaft, which immediately emerged from a panel between Rainbow Dash's legs, as if the pegasus had suddenly sprouted a deep purple penis of her own.

“Awe-some,” Rainbow squeed, giving “her” new member a test stroke with her wingtips. Twilight moaned appreciatively, and trotted over to join Rarity.

Rarity lowered herself as gracefully as possible onto the ground, rolling onto her back and resting her head on a mound in the blanket, and bringing her forehooves up together onto her chest. Applejack clopped around to be standing over Rarity's head, bringing her own rump down towards the fashionista's neatly made-up face. She was facing towards Rarity's tail end, and so her own tail came to rest over the tip of Rarity's horn.

Twilight, meanwhile, climbed on top of Rarity, lowering her own chest down onto Rarity's forehooves and pinning them in place. Twilight's face was inches from Applejack's now fully erect member; She had to tilt her head around to one side just to avoid being poked in the eye.

Even as she lowered her front half, Twilight raised her rump, lifting her dress, flicking her tail forward, spreading her hindlegs, and magically pulling her pussy lips aside to invite Rainbow Dash in. Dash needed little invitation, swooping down behind Twilight, forehooves on Twilight's rump and Twilight's own cock aligned to the bookworm's dripping purple pussy.

There was a moment's hesitation as all four ponies waited for the others to be ready. Rarity breathed in the smell of Applejack's aroused sex, staring up at her vagina and anus. The warm weight of Twilight pressed down on her, the heat of Applejack's thighs bathed her cheeks.

Applejack and Rainbow Dash shared a look, a moment of bonding over the dominant positions they had over the ponies underneath them.

Then Applejack kicked things off by sliding Rarity's pussy down onto the tip of her cock. Rarity groaned lustfully and shoved her face up into Applejack's rump, which came down to meet her, grinding against her muzzle as she pushed her tongue and open mouth in between Applejack's folds.

Rainbow Dash thrust forwards, ramming Twilight's cock into Twilight's pussy with force that made the other mare cry out in pleasure, before Twilight herself stretched her head forward and sucked one of Applejack's balls into her mouth.

The four ponies became a medley of moans and squelches. Rainbow pounded Twilight mercilessly. Before long, Twilight was pumping cum into her own cunt, but Rainbow Dash was unrelenting and the over-stimulated Twilight was somehow staying hard. Rarity's juices ran generously down Applejack's shaft to where Twilight hungrily licked, sucked, and slurped them up. Applejack rocked back and forth, grinding her crotch against Rarity's face and pumping Rarity's pussy down onto her shaft like nothing more than a toy. Beneath them all Rarity shuddered and writhed, needily sucking on Applejack's clit.

Fluids ran down Twilight's legs as she shook from double orgasm, spasms shaking her body. Applejack began to wail as her own orgasms fast approached, her forehooves gripping the Rarity-fleshlight tightly as she instinctively timed the strokes to bring both sex organs to climax simultaneously. Rarity was already cumming, but didn't pause in her attention to Applejack's snatch.

When the farmpony finally reached her own climaxes, she let the tube slip free from her shaft. Ropes of cum arced through the air onto Twilight's head and back, soaking into her dress and mane, dribbling down her horn and face to where her mouth continued to slurp. Twilight began to work her way up Applejack's member as it flopped onto her face, eating up the rivulets of cum that made their way down. Beneath Applejack, Rarity gulped down the fluids that had squirted into her mouth, while still more coated her face.

When Applejack's spasms subsided, she flopped down onto her side, with traces of Rarity's makeup smeared across her hindquarters. As if on cue, Twilight also dropped, all strength leaving her hindlegs as she finally allowed them to un-tense. That left Rainbow Dash standing over her and Rarity, with Twilight's mostly flaccid but still thick and heavy cock swinging between her legs, dripping fluids onto the dresses of the mares huddled together below her.

As the only pony not currently collapsed from exhaustion, Rainbow Dash took it upon herself to make the next move. Jump-gliding her way up to where Twilight and Rarity were cheek-to-cheek smearing various fluids onto each others faces, she swung Twilight's member down to the vicinity of their lips, posing herself cockily over them.

Without needing a work, Twilight reached up and slid a tongue around the rim of her own cock-head. She reached up one hoof onto Rainbow Dash's leg to pull her closer, and Rainbow happily obliged. Twilight shuddered as she got to lick her own mixed cum and pussy juices off her twitching shaft, while Rainbow watched hungrily. Seeing what was happening, Rarity lifted her head and began to assist Twilight's attempts at autofellatio. The two mares slipped their mouths and tongues up and down the length of Twilight's shaft, brushing muzzles against each other and swapping glances into each other's eyes. At one point, their horns collided and slid over each other — when they did, a blob of Applejack's cum from Twilight's horn stuck to Rarity's, stretching out between them as they continued to slide their heads up and down. Twitch by twitch, Twilight's member began to stiffen once more, preparing for another round. Rainbow Dash slowly swayed her hips, rubbing Twilight's cock against the two mares' faces.

When it was almost fully hard, Rainbow Dash pulled away and swung her head around, her body mostly now occupying the same position Applejack had held previously. She used a wingtip to gently hold the back of Twilight's head, and looked down at Twilight's face, with its smeared makeup and plastering of Applejack's cum. Twilight looked back up at her, straight into her eyes. Saying nothing, Twilight understood and eased herself into a slightly straighter position, tilting her head back and opening her mouth wide, angling her own throat straight towards her own throbbing shaft.

Grinning, Rainbow Dash slowly and gently thrust forward, only gently gripping the back of Twilight's unresisting head as Twilight found her mouth filled with her own cock, which was already making advances on her throat. Twilight groaned at the wondrous feeling of being autofellated.

If Rainbow Dash had thought things through a little more, she might not have been surprised when Rarity reached up and planted her mouth onto Rainbow's vulva. Not that Rainbow Dash had any objections, but that didn't stop her from gasping and twitching with surprise, thrusting a little deeper into Twilight's throat than she'd planned to do at this point. Fortunately Twilight seemed to have no problem with this, in fact taking the opportunity to push forward, taking her shaft deeper still.

Rarity, too, was a little surprised to feel a tongue probing her nethers. Not wanting to be left out, Applejack had rolled the cylinder up to her face, and was now having a taste of her own spunk mixed with Rarity's marecum. Well, Rarity didn't have any objections to that, either.

Rarity did her best to match her head bobbing to Rainbow Dash's thrusts, but it quickly became apparent that everything worked out better if Twilight did most of the thrusting, so instead Rainbow opted to help her along, gripping Twilight's head more firmly and driving it down onto the cock. Twilight greedily swallowed her own shaft, eyes rolling from the pleasure. Rarity pressed her face in deep against Rainbow Dash's marehood, intensifying her licking as Rainbow Dash began to quiver.

Rainbow came first, having been waiting on edge the longest. She shuddered and squealed but Rarity continued her ministrations, intending to coax at least two orgasms out of Rainbow Dash before she relented. Rarity herself was second, wrapping her thighs tightly around Twilight as her climax began crashing through her.

Between Rarity's firm grip and Rainbow's spasmodic thrusting. Twilight herself was not far behind. She grabbed Rainbow's buttocks and held on tight as she unleashed her own seed straight down her throat and into her own belly. Her orgasm was the shortest of the three, though, and she soon after collapsed, sliding off her own dick once more, this time coughing and gasping as her lungs burned for air.

Rainbow Dash fell onto her side, but Rarity followed her, working out her own orgasm by helping Rainbow achieve another. Rainbow Dash writhed on the barn floor as Rarity locked forehooves around her hips, Rainbow's hindlegs gripping Rarity's head tightly. Only when Rainbow's quickened panting and moaning, and the spasming of her cunt, signified a second orgasm, Rarity let go, allowing Rainbow Dash to reciprocate in her own time.

Twilight and Rarity lay side-by-side, both exhausted, both covered in sticky fluids, their dressed ruined and their manes disheveled. Rainbow Dash was panting, satisfied but not yet exhausted, while Applejack was already mostly recovered, and quite hard again from what she had just witnessed.

Not wanting to leave her friend out, Rainbow Dash crawled over to Applejack, placing her lips onto the farmgirl's tip and working saliva around. Since Applejack was mostly lying down, Rainbow maneuvered around into a sixty-nine position without thinking. Twilight mewled as Applejack began to tease her now completely flaccid member.

Rarity pulled over the discarded cylinder that held the portal to her pussy. She wasn't really planning to do anything with it. Not much anyway. Just a few gentle “cool-down” licks as she watched the scene unfold.

Applejack had pushed herself into a more upright, seated position, forcing Rainbow Dash to raise her rump high. Rainbow had Applejack's shaft well into her mouth and making inroads into her throat, working her way up and down with singular focus. Twilight lay curled up and rocking on the barn floor as Applejack coaxed her into yet another erection, but she made no effort to protest or ask the farmpony to stop.

As Rarity watched, Twilight's shaft regained a half-erect stiffness, and Applejack took the whole thing into her mouth. Rarity couldn't see, but could well imagine, Applejack's tongue swirling around as Twilight's shaft grew thicker still insider her mouth and throat.

When Rainbow Dash had managed to take the entire shaft into her face, Applejack straightened further, spreading her legs and lifting Rainbow's hindlegs clean off the ground. Rainbow's eyes went wide and her hindlegs kicked the air as Applejack lifted her and began to bounce her up and down — Rainbow Dash stretched one wing up between her hindlegs and began to masturbate. Still curled up, Twilight seemed unable to tear her eyes away from the pair of them.

Gulping, sucking, squelching noises filled the barn. The other girls watched Rainbow used like a sex toy while Applejack deepthroated Twilight's cock. When Applejack came, cum bubbled out of Rainbow's nose and around her lips. Her hindlegs crossed and shook in midair as she reached her own climax. When it was over, Applejack had to help Rainbow Dash down gently so the normally athletic pony wouldn't simply fall and injure herself.

Twilight sighed. She hadn't cum again, but she was too exhausted to push for another climax. Instead, she reached down and removed her belt, pulling her stallionhood out through the portal.

“I…” she gasped, “I think that's enough, for me.”

Rarity was enjoying playing with her own cunny, but had to admit she was too worn to really get invested in it, so she set the cylinder down and murmured assent.

“Yeah, I'm good for now,” agreed Applejack.

Rainbow Dash raised a wingtip in a gesture of affirmation, still collapsed on the floor.

…

By the time the other girls had recovered, Rainbow Dash had fallen asleep. They left her on top of a hay bale; She could take care of herself when she woke up. Twilight offered to teleport herself and Rarity straight back to the boutique's bathroom, and Rarity all but leapt at the suggestion. Figuratively, at least. They stayed to help with the cleanup, first, but with Twilight's magic and Applejack having planned ahead, it didn't take all that long.

Back at the boutique, the pair showered together. Rarity's belt was removed, all the devices set aside for cleaning. Afterward, Twilight gathered up her research notes, thanking Rarity for being such a helpful test subject, and explaining that she would be returning home to compile her results.

“Very well, darling, but… would it be too much to ask, if you could lend me a couple of those devices? Whenever is suitable, of course.

“I have a few experiments of my own, that I'd like to run…”