Alphys:
Oh god. Oh. God. A cell phone clatters to the floor, knocking over a few noodle cups, as a short, lizard like monster buries her face in her hands. She can't believe all of what just happened, nor what she just instigated. Breathing deeply she thinks back to the beginning of this whole debacle.

Not too long ago she had noticed on her cameras that someone had came to the Underground. A human to be precise. She'd watched and planned and meddled with their journey and even met with them to help in Hotland. Despite what she initially suspected the human turned out to be nice. Very nice in fact. That made it a no brainer to accept going on a date with them. She learned however that it was actually Undyne who wrote the letter when she barged in on the date and dunked Alphys into a trash can. Undyne was always dreamy like that. But she couldn't help but think about that cute human helping her out with her date. Or that obscene bulge she noticed in their pants that reminded her so much of Undyne's.

So that brings her back to now. She'd just gotten off the phone with them, requesting they come to her lab for more confidence testing. She knew it wouldn't be long now before they arrived and she was preparing herself, slowly riding one of the many dildos she had hidden around the lab.

Frisk:
Let's get one thing straight. Being a human in an underground world /full/ of monstergirls can be both a blessing and a curse. On one hand you get more than enough material for masturbatory sessions. On the other the only one interested in dating you is a skeleton bro. Not exactly in Frisk's top 10 sexual fantasies. But the ambiguously gendered human pressed on, treating their visit to the strange new place as a chance to make friends and hug walking volcanoes and whatnot. They even agreed to Alphy's fake date, and while Undyne had come and interrupted it before anything fun could happen Frisk curiously but hopefully accepted the invitation to meet up again back at the lab.

Standing before the large lab doors, Frisk briefly adjusted the sizable protrusion in their pants, making it seem like someone had stuffed a basket ball in their jeans. Likely Alphys just wanted to watch that god awful anime show but maybe there would be time to sneak into that bathroom and jerk off. Forgoing knocking Frisk simply entered through the automatic doors, walking in on the yellow lizard sitting at her desk and looking even more flustered and red in the face than usual. Eh, nothing new.

Alphys:
Alphys nearly jumped out of her skin when she heard the door to her lab open, scrambling to get off of the dildo and hide it. A daunting task considering it was at least two feet long and as thick as her arm but she managed it, sitting awkwardly back down on her chair right as Frisk walked in. She turned a little too quickly to meet them and nearly spun herself off of her chair. "* O-o-oh you're, um... Early. Th-that's good though! It means we can, uh, get started sooner." A broad, dorky grin crossed her face as she stepped off of her chair, lab coat fluttering a bit from the movement, inadvertently showing off her thick legs.

Alphys stood still for a few seconds and rubbed her hands together, glancing around the lab and trying her hardest not to stare at Frisk's bulge. Which was just impossible really. Her eyes were drawn to it more than a few times and a blush was already forming on her face. "* S-so, uh... Where to start with the confidence boosting." She thought for a few seconds before an idea popped into her head. "* Wh-why don't we watch some anime... together? I found some new ones you m-might like and... Maybe talking about them will help my confidence?"

Frisk:
Yep. Still an awful, awkward nerd. At least the adorable kind. Frisk wasn't exactly sure how they could be early considering the Underground didn't really have a day/night cycle, so they just shrugged it off and nodded, their face an enigma as always. Watching Alphys stumble about was pretty amusing though.

"* Confidence boosting? Right." Frisk said in an average voice, nodding at the lizard. Honestly Frisk didn't have much of a clue why they had been invited, but if Alphys wanted it to be some kind of pep talk thing then they would oblige. Even if it meant watching anime, which isn't real, by the way. "* I guess that anime will be Mew Mew: Kissy Cutie then?" Frisk almost couldn't forgive themself for remembering that title but as much as Alphys harped on about it, it didn't come as much of a surprise. Neither did the fact that Alphys not-so-discretely seemed to eye their crotch as she hadn't been the only one in the Underground doing so.

Alphys:
It made Alphys extremely happy that Frisk remembered the name of her favorite anime, nearly foregoing her plan to watch that with them. But she knew she couldn't do that. Taking a deep breath to calm herself she started fiddling with her hands again. "* A-actually I found some new anime when I was walking back here from out... d-date." A deep blush crossed her face and she cupped her cheeks, looking extremely anime herself at the moment. But she stopped a moment later, chuckling to her own silly antics. "* Anyway I don't want t-to keep you too long so... let's just get to it!" Before Frisk could react Alphys had walked over and grabbed their hand, pulling them along behind her as she rushed into her room. Oh this was going to be fun for sure.

The two of them walked out an hour or so later and Alphys did indeed look a bit more composed than before, a broad smile on her face. "* S-so what did you think? I mean, uh, about the anime of course. Not my room." She can't believe she had managed to do that. Sit alone with someone and not make a fool out of herself though maybe that was because she needed to keep her composure. After all she had snuck a few tapes of hentai into the session to try and entice Frisk and also herself, feeling her tail wiggle a little bit in arousal. "* I did kind of lie about the tapes though. Not all of those were new... or anime."

Frisk:
While Frisk had to admit that they weren't exactly an anime connoisseur, they knew a good show when they saw one. And they also knew a hentai when they say one. Someone must have thrown away a whole heap of XXX rated DVDs and while old a tentacle shoving itself into a hot woman's hole is still a tentacle. Which made it veeery difficult to not mention it to Alphys, though not nearly as difficult as it was keeping their boner down. With Frisk's size and girth they had to constantly keep a hand on their crotch, which might have been why Alphys hadn't paid as much attention to the "anime" as expected.

Once free of the torture, Frisk had managed to calm themself down enough to only be a bit frisky, and despite all evidence to the contrary Alphys genuinely seemed to have been interested in watching anime and not having sex or anything like that. Welp, time to find a bush or something to jack off behind, because now Frisk really needed it. "* Eh uh what?" Frisk's train of thought was broken by Alphys, who confirmed the obvious. "* Yeah, I think I noticed. Normally most animes leave the protagonists with at least some clothes on. I guess it's alright, at least the girls seemed to have fun getting fucked senseless." Shrug.

Alphys:
Alphys nearly stumbled when she heard Frisk just blatantly say through them not being animes. Did she really think someone wouldn't notice those weren't normal animes? Still the ploy had worked for the most part. The two of them did watch anime, and hentai, together and Alphys was feeling more sure of herself. Even if that might have been from the budding arousal she was experiencing. "* W-well I hadn't expected you to know of that stuff... but that's okay! It m-makes talking about it easier right? Like when the main character-" Alphys quickly got to talking at length about the hentai, and anime, that they had watched. Of course it didn't take long for it to be exclusively about the hentai and her voice took a turn for the sensual.

As she spoke about the hentai it wasn't hard to notice something happening with her body. Namely that her tail was ever so slowly lifting up. Alphys didn't even seem to notice it happening, just standing stock still in front of Frisk as she spoke, it apparently being subconscious. Normally this wouldn't be a problem if she were by herself but her tail was lifting up her lab coat, showing more of her legs. Oblivious to her tail's actions it didn't take long before Alphys' legs were exposed, showing Frisk their thick but curvaceous form along with the part of her colossal butt cheeks and hips. However something seemed off. With her coat pushed up so far Frisk could no doubt see something pressing into Alphys' tail as it lifted up.

The moment her tail was all the way it was abundantly clear what that was. A thick, yellow ring swelled out from between her ass cheeks and pressed into the base of her tail. It was smooth and glistening in the light slightly even with her tail's shadow on it. Mostly because it was wider than her tail was and at least a quarter of its length, pushing her cheeks apart. The most eye catching thing however would be the big, bold words printed on this curious ring, above and below the opening at its center: ANAL ONLY.

Frisk:
As Alphys launched into a tirade about anime Frisk opened their mouth to intervene, only to stay quiet and stand there, a tired if indifferent look on their face. Guess the torture wasn't quite over yet. At least Alphys had a hearty interest in something, that couldn't be said for all people. With Frisk's attention drifting from anime it eventually found its home in looking at Alphys tail, if only because that was the one thing moving that wasn't her mouth. 

The hentai had done more than enough to make Frisk horny and at the sight of the lizardwoman's thick legs they couldn't help themself from biting their lip, adding that to the list of things one could fantasize about. But they wouldn't need to fantasize since the tail only kept on going up, and since Alphys was so busy blabbering Frisk took the freedom to discretely sidestep her, if only to get a better view of that round ass. And it was worth it, the yellow orbs impeccable in shape and form. 

But it was then Frisk saw it. Swelling outwards, no longer held down by her thick tail, a large, fat ring began to show, expanding outwards and pushing her cheeks apart further and further the higher up the tail got. Frisk found themself right behind her with neither of the two realizing it, only capable of starring as the huge and moist hole presented itself, rounded by the plushest anus they had ever seen. Suddenly the tip of Alphy's tail was in Frisk's hand, pulled upwards entirely so that the asshole was out in its full glory, and the human's pants were now looking like they were about the burst open from the gargantuan cock within. "* Shit!" Snapping out of it Frisk dropped the yellow member, quickly scrambling to undo the pants and letting out a log of a dick out, the thing flopping down past their knees and as thick as a thigh. "* ... Fuck. Sorry."

Alphys:
Alphys just couldn't herself when it came to discussing hentai and anime. She knew for a fact she had been dominating the conversation but, really, that was the point of this endeavor right? To get her to be more open about things? In fact it would have to take something pretty startling to knock her out of the roll she was on and something like that did happen. She gave a small chirp as Frisk grabbed onto her tail but all that really happened was she stood there in silence. "* H-hey! W-warn someone if you're going to g-grab their tail... Are you just getting a f-feel for what a monster tail is like? Since n-no one else you've met has one."

A deep blush was on her face as she remembered the feeling of Frisk holding onto her tail, grinning a bit at the exclamations afterwards. That was what she had expected the cursing was for, completely oblivious to the fact her asshole was out in the open now, flexing gently, still glistening tantalizingly in the light. An idea popped into her head and she gave a small grin to herself. Frisk must have gotten a bit aroused from the movie and was now wanted to take it to the next level! Of course she couldn't understand why they would be attracted to her tail. Maybe humans were just like that? She figured the best option was to try and flirt back. "* I-it's pretty, uh, big isn't it? I th-think I have the b-biggest one in the whole Underground. Even Undyne is i-impressed by it! And Mettaton w-wanted me to put one on h-his body but... I don't think it would have worked out. Y-you can touch it... if you wanted to."

Frisk:
For someone with an enormous asshole like that it was frankly surprising that Alphys could be so oblivious, though Frisk was not going to complain about getting a few more precious moments to gawk and stare. They thought that Alphys was going to be mad when she chastised them for grabbing the tail, but apparently she was more than okay about it and Frisk realized that even with the tail sinking back down slightly the donut was still visible.

Yet Alphys wasn't finished with her surprises and Frisk thought they'd start nosebleeding when she mentioned that they were allowed to touch it. The human had never experienced such a hard-on before and after having spent so, so much time in the Underground they were so incredibly pent up that if Alphys was willing to offer her body for a fuck, then they'd damn well take it. "* Hell. Yes. I think I'll even do more than just touch it." Frisk grabbed the tail and lifted it once more, exposing the inviting asshole once more, but instead of fondling the yellow member as Alphys had expected Frisk roughly stuck a thumb straight into her anus, using it to stretch the ring open and see how pliable it was. Their other hand began to grope and feel the glistening flesh, wasting no time to enjoy this new opportunity.

Alphys:
Even more than just touch? Alphys wasn't quite sure what that meant but she was excited and more aroused. Frisk barely even needed to move her tail as it had already started lifting itself back up but it did make her think they were actually after her tail. Gulping she thinks to herself and tries to come up with something that might entice Frisk. What exactly could she do with a tail? Thinking quickly she started to wiggle her hips back and forth, causing her tail to swing in the air. More importantly though it made her ass and asshole jiggle excessively, her cheeks lightly clapping together, muffled by her meaty anus being in the way. She couldn't help but blush at how that much have looked, her asshole puckering in and and out in nervousness and arousal. For a moment she wondered if Frisk was enjoying her tail but what Frisk did made her realize they weren't interested at all.

Her mouth opened wide as Frisk's thumb wedged itself into her pucker and an airy gasp came out. For the most part she was just stunned. They hadn't been interested in her tail! They were interested in her... Alphys shook her head a bit to try and regain some of her focus but Frisk's continued squeezing of her asshole made her lose every train of thought she had. Unsurprisingly it was hard to talk when someone's thumb was jammed in your butt. Still she can't just sit here and take it. She had to say something. "* H-hey!" Her voice trailed off for a second, unsure of what to say. "* You aren't f-freaking out. Don't I l-look like a total... slut? W-with that h-huge, fat hole j-just... sticking out back there! Isn't it g-gross? It's a-all sweaty..."

Frisk:
"* Too rough?" Frisk wondered at Alphy's sudden outburst, though their fingers did not leave her anus, not on the outside nor the inside. They did slow down a little though, but it was impossible not to squeeze and knead the doughy anus, glistening with perspiration and looking hot as hell. 

"* I think it might be a bit slutty to tattoo your ass like this but honestly? It just makes it look even better. I've never seen one so plump and huge before..." Biting their bottom lip Frisk crouched down to get a better look, putting their head at the height of the gaping hole. Fuuuck they /really/ needed to stick their dick in that. But not before Alphys was teased some more, which was easily done by stuffing a few fingers into the tight ring, threatening to have an entire fist slip in were she not careful.

Alphys:
Alphys couldn't help but blush as Frisk talked about how much they were enjoying the sight of her pucker. It was a bit of mind bender. She had always thought that someone would find it strange or gross, not the hottest thing they'd seen. That filled her a bit with pride though she really wished that it wasn't entirely accidental that she showed it off. Not that she'd have actually showed it on her own. Maybe this was the best option after all. her rambling thoughts are cut off as Frisk stuffs a few more fingers into her pucker and she lets out a wavering moan. Her asshole puckers up again in arousal and inadvertently swallows up Frisk's hand as well as a bit of their arm before pulling back, Alphys shuddering at the sensation.

Taking a deep breath she started to speak again, her voice still stuttery. "* Th-thank you for the... compliment. You c-can, uh, touch it more if you wanted. L-like, uh, grabbing a wh-whole handful... or putting in y-your whole h-hand." Her voice trailed off for a second and when it came back it was firm and deliberate. "Y-YEAH!!! DO WHATEVER YOU LIKE TO IT!!! GIVE THIS ANAL SLUT WHATEVER YOU'VE GOT!!! WHY DO YOU THINK I HAVE THAT TATTOO?!? I'M ALL ABOUT GETTING MY ASS STUFFED!!!" And the moment she finished her outburst Alphys' face was buried in her hands, letting out a displeased groan at herself. Now she just wishes she could crawl away.

Frisk:
Even Frisk, someone who almost always had a neutral face, had their eyes wide open at the sight of their hand being slurped into the fat pucker, with enough force to get some wrist in as well. The sweat was understandable from how warm she was inside, and as the hand got pushed back out Frisk did not miss the opportunity to push it back in, feeling the plush insides of her rectum.

But at her sudden outburst it became clear that just a fist wouldn't be enough, and honestly Frisk wasn't exactly getting off on that either. It amused them that Alphys had been too ashamed to look back during all this time but that also meant she would get to experience how Frisk cock felt before she saw it. "* Whatever I want? Alphys, sometimes even you need to enjoy yourself." Pulling their hand out, Frisk grabbed one of Alphys' buttcheeks in each hand and spread them wide, the fat pucker invitingly poofing out and present itself to them. Their dick was aching to be used but they weren't going to miss an opportunity to play with such an amazing thing. Grinning, they crouched down under the tail and allowed themself to stare at the flexing ring, licking their lips at the sight. Unable to help it Frisk pushed their head forwards and noisily began to lap at the inner circumference of Alphy's pucker, pressing their lips to the fat donut and feeling its softness.

Alphys:
Oh this was so humiliating. So awful. She just screamed out, without any shame, about how much she wanted her ass reamed, played with, fucked, touched, and everything in between. There was no way Frisk was going to be okay with that. They had to be fed up with her now. Just as she's about to say something Frisk begins to speak and Alphys stays quiet, just listening to them, her asshole flexing with her breathing. It took her a few more seconds to respond, thinking about what to say. "* M-maybe. It would b-be nice... but I'm so-" She didn't get to finish her sentence.

As she spoke Frisk's hands grabbed onto her ass cheeks and spread them apart, making her gasp loudly. Her pucker wobbled gently and flexed excitedly, swelling out more from not being compressed. She couldn't imagine what Frisk had planned. Were they just going look at her asshole more? Rub it deeper, closer to her actual ass? Her question was answered when she felt something warm and wet press against her hole, letting out a sharp gasp and straightening her back. "* W-wait! A-are you..." With the tongue pressing against her her voice trailed off again into a moan, Alphys shuddering gently. That meaty anus was still twitching frequently, pressing against Frisk's face, even almost pulling it inside. But she wasn't going to do that, not wanting to weird out Frisk.

Frisk:
Since Frisk seemed to have no problem with an anus that was the size of their face, it did not seem like they would have any difficulties with any strange properties relating to it either. They seemed happy to continue to lap on the yellow donut, pressing the tip of their tongue into the edge of the soft pucker and getting it wet with saliva. Every now and then their tongue teased the entrance as well, circling around its perimeter and thrusting inside only to pull out as fast.

Frisk also had needs however, so to solve this they might as well get the best of both worlds. Letting go of both of Alphys' cheeks at once, their hands went down and began to jerk off their throbbing, needy rod, stroking it rapidly just to relieve some of the pent-up horniness that the fat anus had caused. That didn't mean they stopped their ministrations however, though now they had to push more with their face to be able to lap at the juicy ring, Frisk getting their own face pretty wet with saliva in the process.

Alphys:
Alphys lets out a small gasp as her ass cheeks are let go of, clapping noisily against her asshole and Frisk's face. The force made her pucker wobble a little against Frisk's tongue and the extra stimulation made her moan softly. Of course with her cheeks back to where they were it was putting a bit of pressure on her anus, squeezing it so Frisk had to reach deeper to get it. Alphys just couldn't let them work harder while she just sat that. "* H-hey. I'm going to help a bit." Her arms slowly reach back to her butt cheeks and grab onto them heartily, Alphys biting her bottom lip as she spreads them apart. Her doughy anus surges forward once more and presses against Frisk, only this time it keeps pushing and swallows up their head. She lets out a sharp, flustered gasp and pulls herself forward, her asshole audibly popping off of Frisk's face, flexing open and closed energetically. "* S-sorry!"

Frisk:
It was evident that Alphys' asshole was one of incredible pliability, but even Frisk was surprised when suddenly it surged forward, pressing against their face and then some more. Their head got smeared with their own spittle and as the anus slid off again they took a moment to wipe their fringe, if only to keep themself from looking silly. "* It's... Alright." Frisk was only jerking off harder at that point, precum flicking off to land between Alphys legs, some even hitting her shins and thighs. 

Being swallowed up by a fat, squishy anus did not deter Frisk in any way thankfully and with Alphys spreading her own cheeks there was no reason not to dive back in, Frisk pressing their face up against the donut to the point of risking getting pulled back in again. Eventually they pulled back, the yellow ring gleaming and making various squelching noises whenever its owner clenched or stretched it open. "* Ah, there. Do you think that's gonna be enough?" To test their work Frisk thrust in a few fingers into the slimy hole, which quickly turned into a fist with seemingly no difficulty.

Alphys:
Well at least Frisk wasn't mad with her. That was a bit relieving. She was still nervous of course, especially with her asshole puckering frantically behind her due to her nerves. At least it was a hot sight, something she'd watched herself do in the mirror before. "* E-enough? I mean... I'm still as h-horny as when we started! Well that's not true... I'm even hornier now." To emphasize her asshole gave a hard shudder as it closed up only to be penetrated by Frisk's fist, making Alphys gasp sharply. "* O-oh! For fisting you m-meant. Yeah it... Feels like it should be enough? Just, nnn, keep doing that. Please. It might n-not be enough to fill be but... it's great!" While the tongue was definitely a wonderful sensation actually getting penetrated was so much better. Alphys was letting out barely audibly moans and gasps, trying not to make herself look too needy, more for her own sake than embarrassing Frisk or anything. Plus how was Frisk ever going to satiate her incredibly hungry anus? They'd have to go find her biggest toys and she couldn't wait that long.

Frisk:
After a few pumps of their fist Frisk agreed that it should be more than plenty "lube", pulling out with an obscene squelch. Alphys asshole was so incredibly inviting, gleaming in the lab light and flexing open and shut, saliva drooling from the opening. "* Don't worry, I should be more than enough to fill you." Frisk's hands returned to her asscheeks, taking over spreading them apart since they doubted Alphys would have the sense to keep holding them once they begun. Frisk's thick cockhead began to circle the squishy entrance, feeling the heat of her fat donut before they thrust forwards, finally sinking several inches of prime fuckmeat into her depraved anus. "* Ooof! That's -heavenly-!" Frisk moaned and took another step forward, getting more of their dick inside the lizardwoman.

Alphys:
"* Y-you should be? What do you..." Alphys gave a gasp as Frisk's hands grabbed onto her ass cheeks and she did indeed let go of them. Mostly just to let Frisk do what they wanted with her ass. They hadn't disappointed so far after all. Nervously she fiddled with her hands as she waited for Frisk to do whatever it was they were planning. But she was entirely caught off guard when their massive prick pushed into her asshole, stretching even that fat ring out. She let out a long, wavering moan and finally turned her head around to look, eyes nearly bulging out of her head. "* O-o-oh my g-god! That's s-so... BIG! W-were you always like that?" A gush of fluid ran down her thighs and another moan escaped her lips, asshole flexing heartily around Frisk's intruding cock.

Frisk:
Frisk couldn't remember ever having thrust into a hole this tight and plush, Alphys' anus squeezing their cock from all angles and rubbing against it with delicious warmth. "* Yeah!" They moaned out and pushed another inch inside, knees shaking as the asshole clenched and pulled them in further. Maybe covering the donut with spit had been unnecessary since Alphys seemed capable of taking the dick remarkably easy. Easy enough for Frisk to grip onto her waist and, with a strong tug, pull the yellow monster's butt so close that they could feel the slick anus press up against their crotch and balls. Frisk had misjudged the weight of that thick ass though and ended up stumbling, falling to the floor with a thud. Not that it mattered, since with Alphys sitting in their lap anything but her amazing anus was quickly forgotten.

Alphys:
"* I f-feel so dumb for n-not noticing before... But I guess I wasn't really looking? B-because that would be..." She mumbled to herself right after saying that, trying to excuse her having not looked and realizing halfway through she did the right thing by not staring at someone's dick through a camera while they didn't know she was there. The debate she was having with herself was cut short as Frisk yanked her hips backwards, making her gasp sharply as they hilted fully inside of her. Of course that's when she realized she wasn't on her feet anymore, tumbling backwards and right back onto Frisk's lap, letting out a grunt as her butt cheeks jiggling from the force. For a moment she tried to pick herself up, sliding her slick asshole along Frisk's cock, before falling back onto their lap. That's when it hit her. "* O-o-oh my god! Are y-you okay? Y-you aren't hurt right?"

Frisk:
This was going to be good. Frisk was experiencing pure ecstasy as the plush donut dragged up along their shaft, squeezing the girthy member deliciously before suddenly and unexpectedly thrusting back down. They had to let out an audible gasp as Alphys' ass pressed back down against their crotch, thick cheeks jiggling against them. "* I'm fine! I'm fine. Fuck..." Biting their lip Frisk began to gyrate their hip, stirring up Alphy's insides with their massive pole of fuckmeat. "* D-Do that again." To assist their hands went to Alphys' hips and began to lift her.

Alphys:
Phew. At least Frisk was okay. Alphys wipes a hand on her brow and promptly moves both of them to her knees as she didn't know where else to put them. Plus it gave her a bit more stability when she slowly started to pick herself up off of Frisk's crotch which she quickly found she was being assisted with. "* S-sure! But this time I'll be more c-careful." True enough her ascent was laboriously slow, her asshole flexing and rippling around Frisk's dick, until she was standing upright. She looked back at Frisk with a nervous smile on her face and that was when it hit her. Despite the fact she was standing now that cock was still inside of her asshole. Sure not as much as before but definitely enough to feel. Before she can even make a comment, or think too hard about it, the pleasure from it hitting her caused her knees to buckle and her to topple back onto Frisk's crotch, ass wobbling excessively and her anus making a loud squelch as it was suddenly filled with more than a foot of cock.

Frisk:
This was one of those moments where going slow was better than hurrying things along. Frisk audibly gasped as the plush donut began to rise and drag along their shaft, and with Alphys' surprisingly skillful anal muscles the experience was brought from great to heavenly. Her fat tail whapped against their chest as she rose up, now unable to cover its hidden treasure, and it gave Frisk /something/ to hold on to as the pleasure overwhelmed them. Or what they thought overwhelmed, until Alphys suddenly fell back down and rapidly covered the entirety of the cock once more, tensing up and squeezing the throbbing appendage deliciously. Frisk yelled out and arched their back in response, a thick dollop of precum shooting into Alphy's backside from the stimulation. "* Holy FUCK, this is great!"

Alphys:
She could feel each spurt of that hot liquid inside of her and it made her insides tense up, letting out an airy moan. For a moment she just sat on Frisk's crotch and let them hold onto her tail whilst she rubbed her ass against their crotch. Her tail gently swished back and forth while she did so until it lined up with Frisk's face again. "* O-okay. I'm going to do that again now... alright?" She waited just long enough for Frisk to say something before slowly lifting herself up once more. A shiver or twenty went down her spine as she moved and her tail wiggled gently. Once she reached the tip again she took a deep breath and slammed her hips back, swallowing it all back up. However she wasn't done. Rather than sit still she picked herself again, this time a bit quicker, and dropped her ass onto Frisk's crotch until she got it up to a steady rhythm, the sound of her fat ass cheeks clapping into their crotch echoing through the lab.

Frisk:
Having their dick simmer in the sweaty warm confines of Alphys butt was great, but Frisk wanted more out of this yellow monster. Luckily, Alphys was more than happy to oblige. "* Yeah go for it." Frisk grunted, gritting their teeth as the plush donut began to drag up the shaft again. The air in the room felt cold on their exposed dick but Alphys quickly remedied that by enveloping it in her warmth once more. As she kept on repeating her motions, getting to a steady pace, Frisk began to return it by bucking their hips whenever Alphys slammed down, squishing her donut pucker against their crotch with a depraved squelch. Frisk's hands soon moved over to grip Alphys' cheeks, kneading the fat orbs like they were kneeding the human's dick.

Alphys:
The moment Frisk's hips started to meet her own Alphys shivered and moaned loudly, nearly falling back against them once more. She'd gotten so used to riding herself that she'd forgotten Frisk could move too. Feeling their hands on her rump had her get right back into riding, gritting her teeth as she lifted herself up again. Once she reached the tip however she did something a bit different this time. She pulled up just a little farther until the tip of Frisk's cock popped out of her well stretched asshole. Moaning softly she rubbed her plush hole against the mammoth dick wedged between her ass cheeks for a few moments before reaching back to place it back inside of her, sliding slowly down and onto Frisk's crotch once more. "* G-g-god this is so good!" As she spoke her hips got back into their steady rhythm of bouncing once more.

Frisk:
Just as they were getting into it Frisk found Alphys pull off, much to their distaste. It was hard not to thrust up into her squishy butthole and return to its comfortable warmth but before they got a chance to do so she began to rub the tip, squeezing it with her donut while copious amounts of precum spewed forth. By the time she sat down Frisk was heavily panting, staring at her ass in wonder and lust. "* You d-don't say!" they moaned, eager to resume the fucking at an even more rabid pace. With a steady grip on the lizard's hips they roughly thrust her back down, noisily slapping her ass against their crotch while a very familiar and sought-after tension began to grow in their groin...

Alphys:
Alphys gave a sharp gasp as Frisk pulled her back onto their crotch, mostly from surprise than anything else. She gets into it just a moment later though, lifting up her ass and noisily smacking it down on Frisk's crotch. "* I w-wanted to do that before we got moving a-again." She turned her head back for a moment to grin at Frisk before adjusting her feet a bit. Taking a deep breath she leaned herself forward and hefted her tush off of Frisk's crotch, pushing it back down and quickly getting back into her previous rhythm. Only this time she just kept going and going, getting even faster than she had before. She could barely hear herself moaning over the sound of her cheeks slamming into Frisk. However she didn't need to, feeling an all too familiar feeling inside of herself. "* O-o-oh! I'm going to... c-cum soon."

Frisk:
Frisk just had to smile back at Alphys when she grinned at them so cutely, though that facial expression was soon broken by a gasp as she began to pull herself up again. Being the good friend they was, Frisk helped her along and made sure that she got back up to speed, thrusting upwards into her plush behind whenever she would squat down. The lewd slapping noises once again filled the lab and Frisk was having it really difficult to keep going, not when her donut asshole kept squeezing and molding their cock with such amazing dexterity...
The pleasure had been so overwhelming that Frisk forgot to warn Alphys how close they were, the only indication that they were about to cum the fact that they thrust up into her with the loudest smack yet. White, rich jizz began to gush out of their throbbing phallus, balls clenching up tight against their body while unloading jet upon jet of the gooey stuff. With a cock their size it was expected that the orgasm would be proportionally huge and Alphys anus would rapidly be filled with sperm, stuffed full and then some more.

Alphys:
The hands on her ass surprised her for a moment but she gladly accepted them, rolling her hips into Frisk's grasp to let herself bounce harder and faster. Mostly because her cushiony ass and anus were practically bouncing her off of Frisk's crotch before she could even move. Not that she was going to complain. It was bringing her orgasm closer and closer, feeling her thighs steadily wetten from all the moisture. She was gnawing on her lip, aching for release, when Frisk rammed up inside of her. The shock of that knocked off her focus and she stopped moving, landing back on Frisk's crotch. A moment later and she could feel their shaft twitch and spurt inside of them, her insides heating rapidly. Her hands moved down to her belly as she practically felt each shot pound against her belly, tongue having lolled from her mouth as she too orgasmed, fluid rolling down onto Frisk's thighs.

Frisk:
Frisk bucked and spasmed feebly under Alphys weight, bouncing her ever so slightly as they both rode out their respective orgasms. The asshole was milking them for what they were worth and so the orgasm continued unabated for several minutes, much longer than Frisk was used to, before it began to die down. Alphys would sport a belly that made her look pregnant with quintuplets, jiggling between her legs and sloshing with every little movement of her body. The hard lab floor felt like a king size bed with all the ecstasy running through Frisk so they let themself lie there, last globs of cum spluttering out into Alphys hot anus.

Alphys:
Each little bounce Frisk's bucks gave Alphys made her gasp in pleasure, her orgasm dragging on and on. Longer than she'd ever orgasmed before that was for sure. Of course she'd never had anything so big, or so alive, inside of her either. She can feel those heavy shots of spunk pounding against her belly, feeling her orange skin stretch and swell as more and more was deposited. By the time Frisk finishes up Alphys has a dazed but pleased look on her face, just idly caressing her stomach. "* O-o-oh my god... It's so m-much! I guess you were really determined t-to give me a time I wouldn't forget, huh?" Her tail idly swished against Frisk's chest as her asshole still twitched around Frisk's dick, more from pleasure than her actually trying to milk more out.

Frisk:
As the blissful pleasure slowly began to wane the coldness of the floor got more insistent on making itself known and while Alphys was a treat to have sitting in their lap, Frisk didn't want to stay prone longer than necessary. Pushing themself up with their hands into a sitting position, they let out an airy sigh and nodded. "Hooo yeah, really determined." Frisk was just about to suggest Alphys pulling herself off, but then they felt the squeezing. Her asshole was still twitching and clenching, trying to mold the human's cock back into shape without the yellow lizard realizing it... And it was working. Frisk only got half hard before the stimuli got them going again, their erection growing back to full size and eliciting a surprised yet lewd groan from its owner. "And I'm very determined to keep giving to you." Getting up with the help of one hand and holding Alphys with the other, Frisk got on their feet, still balls deep in royal scientist. With her cumgut she had packed on a bit of weight but nothing that Frisk couldn't handle, and her ever-squeezing butthole was enough of an incentive to keep going. "Your room is on the second floor, right?" they asked coyly, starting to make their way over to the escalators while making sure to really slam into Alphys with each and every step.

Alphys:
Alphys of course was having no problem with cold for or anything of the sort, just basking in her afterglow atop Frisk's crotch. That was of course until the human started to move. She doesn't say anything though, figuring Frisk knew what they were doing, but when they commented and began to stand up her eyes went wide. Groaning deeply as they stuffed themselves just a bit deep Alphys weakly wiggled her legs, amazed at Frisk being able to lift her. What was even more amazing was them fucking her while walking to her room. It was a maddening but pleasurable experience, being held up and having her hole rammed again and again. She started to drool when they reached the escalators, which provided a small reprieve, right before Frisk got back into it when they were off. And that was really the last coherent thing Alphys remembered. Of course she knew what happened. The two of them fucked for hour upon hour until eventually passing out, leaving Alphys' asshole gaped open and drooling cum. She thinks she now knows the true meaning of DETERMINATION. And she definitely wanted more.