Undertale - Feeling Horny (NSFW)

Feeling Horny, NSFW, an Asriel/Frisk lewdfic. Frisk has some interests they'd prefer never to see the light of day. Asriel has other plans.

Content warnings: TF, feet/paws, drool, oral, teasing, m/m, touching of the lewd bits, slightly cloudy with a chance of worship, trigger warning: memes.

I blame frick. And tacitly. This really is a monster of a fic, and I'm not sorry.

Word Count: 7892

***

Frisk lifted the shutter with a finger and peered out onto the street. No one.

Not good enough.

Frisk slipped off of the couch and made another round of the house. Every room was dark with the blinds closed, everything was exactly where Frisk had left it. All the bedrooms were empty. Everyone was out, not due back for hours. No one had forgotten anything, there were no phones or keys or wallets promising an interruption, and it seemed like no one was coming back any time soon.

“Okay. Let’s get this over with.”

Frisk checked every lock on their way back to their room. Force of habit. When you lived with magical monsters who could occasionally read your thoughts, you picked up some quirks. When they reached the bedroom door, Frisk was sure to lock it behind them.

The laptop was sitting on the desk. It looked judgemental, somehow.

Frisk resisted the urge to tell the blank screen to be quiet and sat down, cracking their knuckles.

It wasn’t often an opportunity like this presented itself. Frisk wouldn’t trade this new life for the world, but when it came to living with the Dreemurrs in general, and Asriel specifically, sometimes it was difficult to have… Secrets.

Surprising no one, Frisk had developed something of a ‘thing’ for boss monsters. A cursory internet search would confirm that they certainly not alone in their interest. Hell, a cursory internet search would reveal a lot of things, including the materials that got Frisk into this mess in the first place.

It was one thing to want to be with a monster. That didn’t quite scratch the itch for Frisk.

Not this itch, at least.

Frisk called up the website with practiced familiarity. The browser didn’t recognise it, there was no password saved. All of that was habitually wiped clean, the information committed to memory and then hidden behind as many mental barriers as Frisk could erect without arousing suspicion.

It started small. Frisk punched in the names of a few familiar artists and writers with reliably good taste. To their dismay, there was nothing new. Back to the front page then. Frisk grimaced at the wash of raw, unfiltered posts. Good art, bad art, hideous art, outright disturbing art, all of it mashed together with no rhyme or reason.

It was enough to put you right off of your mood. It had in the past. But this afternoon, the thirst was too insistent, it wouldn’t be ignored.

With a sigh, Frisk punched the search terms in. Boss monster. Transformation.

No one could ever know about this. Particularly not Asriel.

Frisk collected a handful of tabs off of the first page and let them load, moving onto the second page in the interim. In no time at all, it was the eighth page, and some of the submissions were starting to look depressingly familiar. It felt like it had been longer, but the unfeeling machine precision of the timestamps laughed at Frisk. They’d barely made it a fortnight this time. Still, a dozen or so tabs of promising leads was better than nothing.

Frisk clicked through, shifting in their seat to get comfortable. This first fic was badly misspelled. The next one was unedited RP logs. One of the tabs contained what had appeared to be a rendered drawing, but it turned out to be a horrific 3d model, lazily posed in front of some pre-made backgrounds. Frisk was pretty sure they recognised the game the environment was from.

Hmm. This one was a story, correctly punctuated and capitalized. A promising start. A cursory glance at the tags confirmed that there were no nasty surprises waiting in the last third of the text. Frisk took a deep breath and started to read.

Damn it. Frisk was almost disappointed. It was good. Not great, not terrible, just… Good. A young girl, out for a night on the town, meets a tall stranger in a bar. He’s rich, which is relevant for some reason, and invites her back to his hilariously expensive penthouse apartment, where he reveals his true nature as a boss monster. He invites her to his room and she accepts, excited but apprehensive. He has clothing for her, for some reason, but it’s the wrong size, far too big. He growls in her ear. Soon it will fit, just right. He bites her, gently, and Frisk rolled their eyes. Boss monsters do not work like werewolves, god damn it. Whatever. She starts to turn, her body shifts and changes, and she does a lot of thinking about how aroused it makes her. Frisk shifted in their seat, reaching down with one hand to undo the button on their shorts.

“...Delicious.”

Frisk slammed the laptop lid shut with enough speed that it blew air in their face.

“God-! Fucking shit! I’ve told you about teleporting in the house, Az!”

“I know, I know. I just couldn’t resist, I can’t get enough of that flustered look.”

“You won’t be seeing much of it with a fucking black eye!”

Asriel put his hands up in a gesture of mocking surrender, stepping back. Frisk huffed and shifted in their seat so they could keep an eye on him, trying to get their heart rate back under control. How much had he seen?

“W-why are you back here, anyway? You’re supposed to be out for the whole day!”

“I wasn’t aware it was forbidden for me to change my mind and come back to my own house, Frisk.” Asriel crossed his arms, a sly grin on his muzzle. He was a little too calm and smug.

“...You planned this? You son of a bitch.”

He chuckled, not ashamed in the slightest. “Oh, Frisk. You wound me. I was merely concerned about you, is all. I could tell you were hiding something, and judging from the efforts you were going to, you weren’t about to talk to me about it any time soon. So, I figured I would just… Create an opportunity.”

His voice was dripping with butter, the tone of voice Asriel unconsciously reserved for his sojourns into dominance and lewdness. The tone set Frisk on edge, although not in a bad way. At least, normally. Why did he have to spring this trap of his now, of all times?

“So you lied to me and your parents to set up an elaborate trap. Well, congratulations, you caught me reading smut. The big secret is out. Now fuck off! I was kinda… In the middle of something.”

“Why would I do that now? We have so much to discuss.” Asriel loomed, reaching for the laptop. Frisk went to place a hand on it defensively, but it was gone. They looked from their hand on the empty desk, and then back to Asriel. He was gone too. The sound of springs caused Frisk to wheel around in their seat as Asriel settled down on the bed with Frisk’s laptop in his hands. Before Frisk had a chance to speak out, he set it down and opened the lid again.

He cleared his throat. “Now, where was I, before you so rudely interrupted… Ah, here it is. “‘And she gasped, running her fingers over the fur, newly grown across her supple…’.” He stopped and raised an eyebrow, looking from the screen to Frisk. “My my.”

Frisk grimaced, burying their face in both hands. “Alright, alright, enough. What do you want, Az?”

“Hmm?”

“What do I have to do for you to keep your mouth shut?”

“Ah. Well, don’t trouble yourself, your little secret is safe with me. For now, at least.” He tapped on the touchpad and the colour of the light the screen was projecting changed. He raised his eyebrows, and Frisk frantically tried to remember what the next tab had contained.

“Okay… Then, why’d you...?”

“It’s simple, Frisk. I want you to be happy. That’s all I’ve ever wanted.” Asriel’s delighted grin softened a little, looking more genuine and warm for a fleeting moment.

“You know what would make me happy? If you gave me back my laptop and went literally anywhere else.”

He chuckled again. “You can have it back, sure.”

Frisk took a deep breath. “But?”

“But! I want you to indulge me for a minute, first.” He leant forward, looking Frisk in the eyes intently. “I want to make this little fantasy of yours real.”

“Nope.”

“Aw, come on, Frisk. This is hardly the first time we’ve played around with magic. What are you afraid of?”

That I’ll like it. Frisk winced as the thought echoed in their mind, covering their face with a hand again. Walked right into that one. “Nothing. I just… I don’t like this. I didn’t want you to find out.”

Asriel glanced from the screen to Frisk, raising an eyebrow. “You clearly like this.”

“Well, I don’t like that I like it.”

“That’s ridiculous! Life is too short to avoid the things you like because of something as pointless as guilt.” Asriel pushed the laptop shut and leant over it, clearly intending to hang onto it for now. “I can help you.”

“I don’t… I don’t want help, Az. I just want…” Frisk’s words died in their throat as Asriel clambered his way over to the end of the bed and patted beside him.

“Just humour me for a moment. That’s all I ask. Come on, come over here.”

“Not until you tell me what you’re up to. And I reserve the right to still say no.”

“You know, you’re being awfully defensive about this.” Asriel said, looking slightly amused and slightly frustrated.

“You set up a sting operation to steal my laptop!”

“Well, if it’s bothering you so much…” Asriel felt around behind where he was sitting and slid the laptop around, picking it up and offering it to Frisk. “Go on, I’m sorry for taking it without your permission.”

Frisk took a moment to surreptitiously re-button their pants before standing up and slinking over to the bed, suppressing the urge to snatch and instead opting to gently take the laptop back and clutch it defensively.

“There. Feel better now?”

“Well…”

“I mean, I can still tell everyone about it unless you do what I say. But you have the laptop back.”

“God damn it.” Frisk put the laptop back in its spot, taking a moment to turn it off before returning to the bed, sitting down next to Asriel with their arms crossed. “Blackmailing goat bastard. This is unbelievable.”

“It’s for your own good! The way you were hiding this, I thought it was this big terrible secret. You had me worried!”

“Is it so much to ask for some fucking privacy? I didn’t want you to know!” Frisk realised that they were shouting, and tried to relax, deflating a little in the process.

“Why not?” Asriel’s voice was quiet, gentle.

“Because it’s… Stupid. Stupid thing that I hate.” Frisk played with the hem of their shirt, realising too late that Asriel knew it was one of their tells. He put his hand on Frisk’s shoulder, and it was comfortingly warm.

“I don’t think it’s stupid.”

Frisk leaned against Asriel and took a moment to breathe, staring blankly at the floor.

“Look. Here’s the deal. I’m relieved that you’re not like, or drugs or something, and I also think this interest of yours is kinda cute, so I wanna indulge us both. I’m just gonna change one thing, just so you can see what it’s like. After that, I’m happy, consider me bribed.”

Frisk tried not to shiver. “A-and, that’s it? You get to play your game and then it’s all over?”

“All you have to do is tell me to stop.”

Frisk considered the offer. Temptation wrestled with guilt. Even if they didn’t like to admit it, it seemed inevitable as to which one would win.

Frisk sighed. “This is like a bad fanfiction. Whatever. Where did you wanna start?”

Asriel brightened up considerably, suddenly all smiles and sunshine. “You’ll find out soon enough! For now, maybe you should lie down. Relax.”

Frisk sighed and shuffled further onto the bed, their quip about relaxing dying in their throat when Asriel deftly snatched their foot by the ankle, gently worked a claw under the elastic of their sock and peeled it off of their foot. Frisk could only stare in fascinated horror as Asriel regarded the exposed appendage, rubbing his chin as though this were a tricky problem for him.

He rubbed his thumb against his fingers, and Frisk felt the familiar, hair raising sensation of magic in the air. It crackled between Asriel’s fingertips, spreading to envelope his whole hand in something that wasn’t quite light or colour, shimmering as though it was hot, but instead of bending the light, it seemed to somehow bend the… Rules. This wasn’t the usual calibre of spell, to be sure. Frisk wondered how long Asriel had really been planning for something like this.

Asriel reached out and lightly ran his fingertips along the underside of Frisk’s exposed foot. The touch was gentle, but it made Frisk shiver and flinch nonetheless. Asriel pulled back, suddenly concerned.

“Oh! Did it hurt?”

“No, I’m just ticklish. You know, like every other person.”

“Oh. That makes sense, actually. I was worried I did the spell wrong. You don’t feel like your flesh is say… Melting?”

“Well no, but now that I’m aware that that’s a possible outcome I’ll be sure to keep an eye out for it you gigantic son of a-”

“Boop.” This time Frisk flinched because they were extremely sensitive on the paw pad that Asriel had just poked.

Wait.

Frisk’s eyes widened as he and Asriel both watched white fur sprout outwards from the line Asriel had drawn with his fingers, the sole of Frisk’s foot already closely resembling Asriel’s, right down to the paw pad on the ball of the foot and the smaller pads on each of the toes. Three of them. Frisk wasn’t quite sure where the other ones had gone off to, but there were other things to worry about at the moment. The fur crept around to the top and met, flowing together and reaching a small way up Frisk’s leg before slowing to a halt.

Frisk wiggled the toes experimentally. They still worked. That was encouraging. Hopefully the other ones were still fine, wherever they’d ended up.

“Huh. Took a second for it to kick in, but check that out.”

Frisk crossed their legs, curiosity briefly overpowering their shame. They ran a fingertip over the soft white fur, poking around the pads and even flicking one of the brand new claws on one of their toes. It all felt normal, as though they’d had a monster foot their whole life, albeit it one with very sensitive and kinda ticklish paw pads.

“What do you think? Should I do the other one, even it out?”

Frisk looked up to see Asriel wagging a finger in front of their nose, the greasy magic still flowing around it. Frisk sighed in defeat and went ahead without him, removing the other sock and tossing it on the bedroom floor to go be with its twin.

“Just get it over with, Az.”

“As you wish.”

Frisk screwed their eyes shut, bracing for impact this time. They managed not to flinch when Asriel touched the other foot, although they were certain he still heard their sudden intake of breath. The tingling sensation rippled across the appendage, quicker this time.

“There. Now they match.” He didn’t have to sound so pleased about it. “You know, I could leave these like this. If you put your socks back on, no one would be able to tell!”

Frisk tried to imagine such a scenario, hiding a secret like this. They touched one of the pawpads again and winced a little, suddenly understanding Asriel’s disinclination towards wearing shoes. It would be terrible, a constant discomfort and reminder. Frisk imagined being flustered and unable to explain why to anyone, and Frisk’s toes curled of their own accord.

“Looks like I hit a sore spot! Maybe I’ll make you keep those, after I’m done.”

Frisk opened their mouth to protest but was cut short by another touch. This time, Asriel ran his fingers up the inside of Frisk’s leg. It was sudden, and more than a little alarming, not in the least because Frisk suddenly realised what would inevitably come next. They barely had time to ponder the lewd implications before he started back down on the other leg, touching at their thigh and trailing the finger tips back down to the ankle.

Frisk leant back, curling their fingers into the bedsheets and bracing themselves before opening one eye, catching the last of the white fur flowing across the last of their skin on both legs. The fur now disappeared into the shadows cast by their shorts. From the waist down, they appeared to be a monster.

“Do you like it? I think it’s a good look for you.”

Despite themselves, Frisk reached out with one hand and stroked the soft fur. Cool to the touch, warm underneath, very smooth.

“I… I don’t know.”

“You look like you know. Although, here’s the real test: Do you want me to keep going up?”

Frisk bit their lip. They wanted to say no, they wanted out, this was terrifying and wrong and awful and Frisk nodded, unable to bring themselves to speak the words. Asriel looked them in the eyes for a moment, the faintest hint of concern in his eyes, before his smile bloomed again and he leaned closer, maintaining eye contact as he reached down with his off hand and unbuttoned Frisk’s shorts once more.

Frisk couldn’t stand the smug look, so they shut their eyes, tensing up when they felt the warmth of his hand against their skin, a moment before the boss monster snuck his fingers into the soon to be ex-human’s underwear, lifting the elastic and gently but firmly dragging it down onto Frisk’s hips. The cool air was slightly uncomfortable, but not as much as the sensation of their erection springing free and bouncing lightly, loudly announcing their arousal.

Asriel hummed his approval, purring deep in his chest as he ran a fingertip lightly along the underside of Frisk’s length. Frisk gasped, squirming on their back gently as the tingling sensation blossomed outwards from the point of contact, rapidly encircling their shaft and travelling out from the base. They were so focused on the sensation that Asriel caught them off guard when he gently poked them in the balls, causing Frisk to jump and squeak, opening their eyes and glaring at him angrily. Asriel grinned, not sorry in the slightest, slipping his hand a little lower and drawing his finger down between Frisk’s cheeks with remorseless playfulness. Frisk blushed and shivered as his finger brushed past their sensitive rear, leaving more of that infuriating tingling in its wake.

“I’m glad you’re enjoying this, Frisk” Asriel purred, gently bopping Frisk’s tip with his finger again.

“Ah! F-fuck you, stop looking at me like that!” Frisk was flustered and embarrassed, not to mention still a little mortified that this was happening at all, but they still had their pride, damn it.

“You’ll have to forgive me for enjoying your… Pleasure. It’s so rare, to see you so unguarded.”

“Well maybe you’d see it more often if you weren’t so fucking smug abo-ooohhaah!” Frisk gasped and glared at Asriel, who grinned unapologetically. He’d crept just a little closer, and now his breath was tickling Frisk’s length. He grinned slowly, baring his fangs.

“You know, you complain a lot for someone so worked up that I can make them squeak by blowing on it.”

“That was- I just- S-shut up! I’m just on edge, ok?”

“Really? Well, I’ll just have to put you more at ease, then.”

Before Frisk could protest, Asriel’s long, prehensile tongue slipped between his teeth, reaching out and curling around Frisk’s tingling cockhead. Frisk barely had the wherewithal to place their hands over their mouth, stifling a moan as the boss monster pressed his advantage, pressing his snout forward and rolling his lips and tongue down to the base of Frisk’s cock.

It was warm, wet, the coiling tongue seemed no less agile for the confined space. Frisk glanced down at Asriel and caught his eye. He had a unique talent for looking gleefully smug even when he was pressing his nose into Frisk’s crotch. Frisk opened their mouth to say something and shifted his jaw slightly, pressing down on their length a little harder and swirling his tongue along the underside, causing them to gasp quietly instead. Frisk decided that talking was a bad idea for now, and rested their head back against the pillow, trying to relax and maybe stop blushing so damn much instead.

Fortunately, there was plenty to take Frisk’s mind off of things. For one, the tingling of magic was more like a buzzing now, permeating the flesh with its intensity, the magic seeming to penetrate all the way through instead of just collecting on the skin. Frisk curled their fingers into the fur on their leg, trying not to whimper as the tingling seemed to penetrate into their core. It didn’t help that their every movement caused their newly unfamiliar paws to shift and brush against the sheets, the silky fabric seeming to be its own unique and new form of pleasurable torment.

Frisk’s resolve broke when they felt Asriel’s tongue snake out and along their balls, wrapping around the orbs gently and giving them a firm squeeze. They groaned, long and loud, reaching out and gripping one of Asriel’s horns and holding his face steady as they arched their back and thrust up against the tongue and maw. They felt Asriel’s tongue shift and retract slightly, and Asriel pulled himself slowly away from Frisk’s length, still taking the time to make a loud, wet slurping sound before pulling away, grinning at Frisk as he licked at the wetness on his lips.

It had an odd sheen to it. Frisk looked from his grin to their cock, which was thoroughly coated in the stuff. The tingling magic feeling was much more severe, now.

That son of a bitch.

“You… F-Ahh!” Frisk let out a gasp as the change started, reaching out to grab themselves instinctively, the tingling spreading to their hands and causing them to pull back, looking at the slightly oily liquid now covering their palms in fascinated horror. Given that this was magic, it was entirely possible that it happened for dramatic effect, but the change seemed to start immediately. The skin under the liquid seemed to… Blur.

The unstableness spread outwards, fading from tan to white, somehow coming into focus as a coating of short white fur which traced Frisk’s form closely enough that they could still faintly make out the lines on their palm as creases in the fur. Frisk closed one hand, rubbing at the palm with the small claws poking out of the alabaster hairs across their fingertips. The fluid was gone, it was dry.

Frisk sat upright, rubbing their fingers together experimentally, fascinated in the details. Asriel cleared his throat quietly and slipped a finger under the hem of Frisk’s shirt, lifting it out of the way so they could both see.

“Oh.”

“Oh?”

“I just sorta… Assumed that monsters were naturally bigger.”

“Why on earth would you assume that?”

“It’s just, you were always so…”

“...Monstrous?”

“Fuck you and your puns. But, I’m…”

Frisk was no longer human down there. The familiar bush of pubic hair had been replaced with a tousled patch of longer white fur, which blended seamlessly into the fur along their thighs. Protruding out of it, their cock was roughly the same shape and size, but now a slightly pinkish white to match the fur. They were vaguely aware that the fuzz around the base extended downwards, covering their balls in a soft white. Presumably it reached all the way around. Asriel leaned forward to get a better look.

“Very nice. You make for a cute monster, Frisk.”

Frisk blushed, dropping their shirt again to hide their erection. “Ah, cram it.” All the fight had long since bled out of them, there was no spirit left in Frisk’s protests. Asriel leant back on the bed slightly, looking Frisk over with no small amount of satisfaction.

When he didn’t move, Frisk eventually cleared their throat and broke the silence. “Uh… S-so?”

“So what?”

“Are you gonna keep going?”

“Frisk. You’ve put up such a fight so far, protesting and squirming all the way, in spite of your own desires and arousal. I’m tired of forcing it on you. I want you to want this as well.”

“You… You want me to beg?”

He grinned, chuckling under his breath. “Mmm. That sounds like fun. But it’s not quite what I had in mind.”

Frisk swallowed audibly. “W-what then?”

“I don’t see why you get to have all the fun. I’ve been working you up and you’ve just sat back and enjoyed it!” He gestured faintly at his lap. “I’m sure you know what to do, to express your thankfulness.”

Frisk realised their mouth was open, so they closed it. They looked from Asriel’s smug expression, to his now very noticeable bulge, and then at their own white, furry hands, before holding them up and gesturing wordlessly.

“Oh please. They still work just the same. It’s hardly the first time you’ve done this, it’s just a little… Different.”

Frisk didn’t know what was worse. That Asriel was extorting them into blowing him in exchange for continuing their transformation, or that they were already crawling across the bed to do exactly that.

Frisk kneeled in front of Asriel, who leaned a little further back and spread his legs to give Frisk better access. Frisk hesitated for a moment, their transformed hands hovering over the boss monster’s shorts, before reaching forward and unzipping him.

“Az. Where’s your god damn underwear?”

He just chuckled. Frisk rolled their eyes, reaching in with two fingers and pulling Asriel’s maleness free of the shorts. They regarded it, looking at the details as though it was the first time.

It was quite similar to Frisk’s new… Equipment. Well, apart from being bigger. Not unreasonably so, but enough that Frisk had gone ahead and assumed that monsters just had more fun, as it were. Still, changing hadn’t made them any bigger, so Frisk supposed that was just down to genetics, such as they functioned for monsters.

It was also, Frisk noted, slightly more pungent. Asriel had apparently been having the time of his life, tormenting them. The proof was slick across the tip of his cock, and running slightly down the underside. He hadn’t moved, trusting Frisk to know what to do. Frisk took a breath, steadying themselves, before reaching out and grasping the base of Asriel’s length with one of their newly furred hands and leaning forward, reaching out with their tongue and touching it to the tip.

Asriel gave a noise halfway between a groan and a sigh, tilting his head back as Frisk slowly lowered their mouth down to the base of his cock. It was warm, it pulsed against Frisk’s tongue and tickled gently at the back of their throat. Even with Frisk’s hand in the way, they’d never managed to fit the whole length in without gagging before. Perhaps later, when their mouth was longer, that wouldn’t be a problem anymore.

Frisk put the traitorous thought aside and focused on the task at hand, swirling their tongue along the underside of his shaft, holding their head on the spot and simply teasing for a moment. All’s fair in love and war, after all. Asriel shifted a hand, the one he hadn’t cast the spell with, and twisted his fingers into Frisk’s hair. He pulled, not too hard, guiding Frisk back along the shaft until their teasing was focused on his tip, and then pulled them back down, starting a slow rhythm. Frisk bobbed along, focusing on their breathing and lips, careful to avoid him with their teeth. Their reward was Asriel’s quiet sounds of pleasure, rumbling in the monster’s chest and occasionally bubbling out as muted gasps. Frisk was sure they heard a bleat, at some point, smiling despite themselves.

Asriel let Frisk’s hair go, leaning forward slightly and panting. Frisk took that as a signal that they should go faster, stepping up from the leisurely pace he had set. There was a wet sound, the panting changed tone, and after a moment, there was a wet feeling on Frisk’s back, causing them to stop and pull away, shivering.

Asriel had his tongue hanging out of the side of his maw. It was gently dripping with saliva, some of which had ended up on Frisk’s shirt and soaked through onto their back.

“Damn it Az, you’re drooling again!” Frisk huffed as they grabbed the shirt and pulled it over their head, inspecting the wet patch on the back before tossing it on the ground for later washing. At least it wasn’t a black stain, this time.

“Huh? Oh.” Asriel reeled his tongue back in, licking his lips and shaking himself slightly. “You were doing such a good job, is all.”

“Well it’s on my back, now. Gross.” Frisk reached back at the wetness, but it was oddly dry. Dry and… Tingly.

There was a patch of what felt like fur back there.

Right. That. Frisk had been so intent on the task at hand, it had slipped their mind that Asriel had added that little bonus to his drool.

Frisk glared at Asriel. He stuck his tongue back out cheekily. Frisk realised that they didn’t have a shirt on.

“Don’t you dare.”

“You wanted to keep changing, right? And you seemed to be having a great time using your mouth. Fair’s fair, Frisk.”

“Az, I swear to god.”

“You don’t need to swear, Frisk. I’m right here.”

Frisk didn’t have time to think of an insult before Asriel moved. He was fast, magically so. The world spun for a moment and Frisk gasped as the wind was knocked out of them, Asriel having half lifted, half tackled them onto their back on the bed. Before they could get their bearings, he was upon them, his long prehensile tongue assaulting their bare chest and stomach, slathering it with layer upon layer of tingling saliva. Frisk squealed, trying to push him away and escape the tickling, but he was relentless, licking at their arms and pushing them aside, pinning Frisk to the bed by their wrists. Laughter bubbled out of them unbidden, Frisk gasping and cursing as they struggled to breathe and Asriel completed his assault, making sure he hadn’t missed any bare skin. The tingling was like a second round of tickling, and it spread around to Frisk’s back and caused them to shiver and pant, still struggling weakly under Asriel.

It finally stopped. Frisk panted, exhausted and blushing, opening one eye and looking up at Asriel. He was looming over them, still holding down Frisk’s arms, looking so pleased with himself. Below him, instead of their familiar chest, there was another sea of white fur.

“Only one part left, Frisk.”

Frisk swallowed nervously.

“I know you like this part. Open wide.” He leant closer, opening his mouth and poking his tongue out again.

Frisk turned their head, still trying to resist for just one more moment. Asriel’s tongue brushed against their lips. It tingled.

Frisk gasped, and Asriel took the opportunity, nudging their head slightly to put them straight and pressing himself against them, his tongue worming its way into Frisk’s mouth as he overwhelmed them. Frisk groaned quietly, huffing through their nose as the tongue tickled against the back of their throat, shivering and wishing that their arousal wasn’t so blatantly poking Asriel in the leg. The appendage touched against the back of their throat again, firmer this time, and Frisk took a deep breath. On the third try, it didn’t stop, slithering even deeper into Frisk’s throat, making their neck bulge and causing Frisk to struggle weakly under Asriel. He moaned into the lewd kiss, clearly enjoying the fight they were putting up as the tip of his tongue wiggled around in Frisk’s throat, causing them to twitch and spasm. The tingling seemed to be consuming their head and filling up their entire chest, spreading to every part of their body. Frisk’s air started to run short, the sounds of their own struggling seeming to fade slightly as the tongue blocked their attempts to breathe, Asriel taking one last moment to enjoy his somewhat stolen kiss before his own throat visibly shifted, the tongue finally drawing back and out of Frisk’s throat, causing them to finally huff for breath through their nose. Asriel shifted slightly, daintily grabbing Frisk’s bottom lip with his teeth and tugging it. It seemed to stretch along with his insistent pulling.

Frisk groaned, still breathless, shaking their head to try and clear their vision. They blinked, crossed their eyes, and realised that the thing in their vision was actually a white snout. Asriel leant back down and gently rubbed his nose on Frisk’s newly protruding snout.

“It’s like looking in a particularly cute mirror! Well, apart from the eyes.”

Frisk slipped a hand free, putting it on his snout and holding it closed.

“Just… Just shut up.”

Asriel continued to taunt Frisk with his eyes, but there wasn’t much they could do about that. Frisk let go of Asriel’s muzzle and flopped back on the bed, exhausted at the extended torment at yet buzzing with both need and what felt like a pretty serious amount of residual magical buildup, almost akin to static electricity that somehow refused to earth itself, instead making Frisk’s new coat of white fur stand on end.

Asriel sat back on his haunches, looking Frisk over, presumably admiring his handiwork. “Hmm. Not bad, not bad at all, Frisk. I quite like this look on you!”

“That’s because you’re a massive narcissist.”

“I’m serious!” He didn’t sound it. “It’s like you were born for this. The perfect partner for me, just waiting to be sculpted and changed from human to monster. Perhaps I could even keep you like this forev-Ah!”

He jumped, startled at the sudden intrusion of a loud, slightly tinny guitar riff. Wide eyed, he patted his shorts and pulled out his phone. He looked from the screen to Frisk and back, wide eyed.

“I-it’s Mum! Oh god, what if they’re coming home? They think I’m out buying groceries! I forgot about the groceries! I’ll be right back, don’t go anywhere!”

Without ceremony, he raised his spare hand and gestured at the air, shimmering slightly before blinking out of existence.

Just like that, the bedroom was empty again.

Huh.

Frisk stared at the ceiling blankly for a moment. A few seconds later, their phone buzzed on the desk. This presented an interesting new challenge for them, Frisk gasping slightly when they twisted on the bed and put their feet on the ground.

Dear god. Frisk hoped the sensitivity was due to the paw pads having never been used before, because otherwise they’d never be able to leave the house again. By the time Frisk made it to the desk, they were already flustered again. They took a deep, steadying breath and checked the phone.

A message from Toriel. Ran into a friend whilst out, having a nice lunch and catch up, Asgore sends his regards and we will be home later than we planned, there are leftovers in the fridge, be good.

Huh. Again.

Frisk sat back in their chair, looking around the room and then back at their laptop. And then from the laptop to their own shorts. The button was still undone, and they were still pretty worked up from the teasing and the change.

Asriel had kind of interrupted, after all.

No, no. That was a terrible idea. It would be gross and weird to jerk off like this. Frisk reminded themselves that Asriel had basically coerced them into this, and that when he got back the first thing they would do would be to demand to be turned back into a human. He’d had his fun, blackmail over.

It was just a matter of waiting. He’d figure out that the parents wouldn’t be back for a while yet, and then he’d come back.

Frisk crossed their fingers in their lap and sat back, trying to ignore the way the fur felt instead of skin. Out of habit, Frisk gripped at the carpet with their toes.

Big mistake. Frisk winced, shuffling in the chair and pulling their legs up to sit cross legged. They inspected the paw pads on the underside of one of their feet critically, going to rest a hand on their chin and missing because they didn’t have one anymore. Frisk huffed in exasperation, patting around on their underside of their maw, looking for a good spot to rest their hand, before giving up on the comfortable slouch entirely. Whatever, bigger problems were afoot.

Frisk gently traced around the curves of the paw pads with a claw tip, marveling at the shape. It wasn’t so bad when they were touching them, but everything else posed a big problem. Asriel could never know about this. The thought of him abusing the sensitivity, perhaps with tickling fingers, or worse, his tongue, it made Frisk shiver and shift, suddenly uncomfortable in their shorts. This wasn’t helping.

Frisk considered their options. Maybe some socks? They did have a pair of stockings as well, maybe that would be better because of the thinner material. Were they a different shoe size now?

Frisk’s mind rapidly began to wander, and they absently rubbed at the foot. A reflex; have paw pad, will pet. Frisk’s eyes slowly closed and they leaned back, reaching up with their other hand to rub as well. It was quite nice, even for a self administered rub. Really nice, in fact.

Without thinking about it, Frisk pulled the other hand back, delicately unzipping their pants and slipping the furred fingers inside, carefully navigating the fabric. They shuffled on the spot, shrugging their shorts down slightly to allow their now erect shaft into the open air once more, slowly rubbing at themselves and continuing to play with the paw pad. Their breathing started to get louder as they stroked, shivering slightly at the sensation of the soft, cool fur against their length and the newly minted erogenous zone attached to their feet. The teasing from before, the oddly lewd rush of this new body, not to mention the forbidden thrill of indulging themselves like this… It wasn’t long before they started to feel that familiar mounting pressure.

“I was gone like ten minutes!”

“Fuck!” This time Frisk actually fell out of the chair.

“Uh, you okay down there?” Asriel peered down over the chair, looking concerned.

“I’m fantastic. Help me up, please. Or go to hell, whatever suits you.”

“Hey, you knew I was coming back!” Asriel protested as he grabbed Frisk’s hand and pulled them up off of the ground. “It’s not my fault you’re incapable of being left alone as a boss monster for longer than a few minutes before you start fapping.”

“This is entirely your fault! If you hadn’t shown up I’d be browsing the internet in a post orgasmic haze, trying to forget about what I’d just done. And I’d still be human!”

“Yeah, because you really look like you’re having a terrible time as a monster.”

Frisk could actually see the blush on their own snout. They silently cursed their traitorous body, reliably terrible regardless of its form. Asriel stepped closer, his nose centimeters from Frisk’s.

“If you wanted a foot rub, all you had to do was say so, Frisk.”

Frisk’s heart actually skipped a beat. The thought from before blossomed into life, the one about Asriel’s tongue.

It would be so easy. All they had to do was open their mouth and say it.

“I can’t.”

“You can’t?”

“I can’t say it.”

Asriel leant back slightly and chuckled. “You know what? That’s fine. Dad tells me that Rome wasn’t built in a day.”

He patted Frisk on the back. Frisk sighed, the moment of temptation was gone.

“He said it took them a few months. Besides, you don’t gotta ask for anything when you’re thinking stuff so loudly.”

That’s right, he can read thoughts.

“When I want to, yeah. My tongue? That’s pretty lewd, even for you Frisk.”

“I can explain.”

Asriel held his finger over the end of Frisk’s snout, taking their hand and gently leading them towards the bed. “Sssh. Just, stop thinking so much and enjoy yourself for once, would you?”

He sat Frisk down and then flopped down next to them, taking a moment to remove and discard his clothing. Frisk took the moment to observe the technique he used to maneuver his shirt around his horns, trying to ignore his ongoing conspicuous absence of underwear. He emerged from the fabric, slightly tousled, looking as Frisk expectantly.

Well, this appeared to be happening, regardless. Frisk finally slipped their shorts and underwear off, daintily lifting the fabric to avoid their paw pads and depositing them on the floor. When they looked back up, Asriel was sitting on the bed and facing them, waiting.

“Go on then, just lie back.”

“What, no gloating?”

“Maybe later. For now, I just want you to enjoy this.”

Frisk just made a low groan of awkward discomfort as they shuffled themselves into position, gingerly lying back with their head on the pillow and their legs still half folded in front of Asriel. He gently took one of Frisk’s feet in his hand, waiting patiently when they flinched at the touch, before gently straightening the leg out and resting the foot in his lap.

He started small, running his fingers under the arch of the foot and rubbing lightly. It wasn’t so bad, it tickled, but it also felt nice against the grain of Frisk’s new fur. Frisk closed their eyes, trying to focus on remembering to breathe. Asriel gripped the foot in both hands, gently bringing his thumbs down on the pad on ball of Frisk’s foot. Frisk let out a soft gasp as he started to knead it, rubbing in smooth circles. In comparison to the sharpness of trying to walk on it, rubbing was much less sharp, instead seeming to generate a tingling warmth which seemed to spread out and envelope the entire foot.

Frisk groaned quietly as Asriel’s exploration diversified, the boss monster clearly becoming more bold as he slipped his fingers in between the toes, rubbing at the soft fur and skin. Despite themselves, Frisk nuzzled back against the pillow, noting the way their new, apparently quite decently sized horns caught at it as they unconsciously flexed and wiggled their toes, right in Asriel’s face.

He took the invitation. Frisk jumped at the sudden sensation of wet warmth and slick, rippling muscle as Asriel’s tongue drew from his heel to the paw pad, ruffling the fur and slicking it down, the touch of it against their pad causing Frisk to gasp again and arch their back against the bed. Given that his mouth was busy, Asriel just chuckled to himself as he set to the task of Frisk’s most forbidden fantasies, working his tongue into the gap between the toe pads and wiggling the tip around, quite enjoying the gasps and moans it produced from his victim. Frisk was visibly hard again already, with no clothing to hide behind, their cock dripping pre onto the longer fur at its base. Asriel caught them totally by surprise when he slipped a hand down the fur along their leg and took a hold of it, lapping at the paw pad and smiling at the way the toe pads tried to clench down on his tongue as he ran his hand along the former human’s exposed shaft, slicking it with their own pre. Frisk shivered, reaching down and putting their own hand on top of his.

“A-ah! Az! Y-You can’t…”

Asriel made a wet slurping sound and pulled his tongue back into his maw. “Oh, but I can. Would you like to cum, Frisk?”

Frisk’s grip on Asriel’s hand tightened. “I, I, uh…”

Asriel buried his snout into Frisk’s paw pad, tickling it with his breath and flicking his tongue out to lick into the deepest, most sensitive parts between Frisk’s toes, all the while continuing his determined teasing of Frisk’s cock.

“A-ah! Yes! God, please!”

Asriel didn’t say anything, he just continued his assault on Frisk’s foot. He nudged his hand and Frisk reluctantly let go, twisting their fingers into the sheets on the bed. It tickled, it tingled, it was difficult to tell where the sensations ended as Asriel began to pump their length, the soft fur on his hand mixing with the sensation of his tongue. Frisk wanted to laugh, to cry, they ran their hand over their own chest and squirmed back against the sheets, feeling the fur on their back and neck brush and fold, the pushed up against Asriel’s hand and curled their toes around his muzzle as their peak approached and their breathing grew rapid and erratic. Asriel, damn his eyes, he backed off slightly, leaving them just on the cusp, shaking and twitching, before he pushed Frisk over the edge, biting Frisk on the paw pad gently as he squeezed down on their cock and pumped it as fast as he could, Frisk gasping and whimpering as they came, catching themselves in the snout with the first jet of cum, the rest of it scattering onto their chest and belly, some of it landing on the sheets, each pulse causing Frisk’s vision to distort and warp at the intensity of the orgasm.

Spent, Frisk relaxed against the sheet, their own tongue hanging out and their breathing ragged. The cum on their snout ran into their open mouth slightly, and they couldn’t even muster the energy to care or wipe it off. Asriel wiggled his tongue one last time, causing them to weakly kick at him, before he withdrew his snout, wiggling his nose slightly. He also finally let go of Frisk’s shaft, much to their over stimulated relief.

“Golly Frisk, you look like you nearly passed out!”

Frisk could only groan in reply. Their limbs felt like they were made of lead.

“I suppose you’re probably not feeling up to more playtime after all that, are you?” He looked down at his own lewdness, erect and ready. Frisk groaned again, the thought of even more stimulation seemed like torture right now.

“I guess you’re right. I can wait, I know what it’s like for a boss monster. You’ll be right as rain within the hour, and ready for another round. But for now, I’ve got something better than just getting off.”

He touched around on the bed behind him and produced his phone.

“Pictures.”

Frisk should have guessed that this was unlikely to be a one time thing. Blackmail was apparently habit forming.

Click.