The loud noise of closing the door echoed in the snow-covered forest, locking anyone outside out of the ominous ruins behind it. While the locals knew about their location, nobody dared to come near them. With few exceptions.
Frisk, a little human girl from the surface shouldn’t be not only in the mystical ruins she just emerged from, but in the underground in general. Thinking that nothing crazier than depressed ghosts and snail-eating motherly goats would happen to her, Frisk couldn’t do anything else but move forward into the unknown.
While her surroundings were covered in thick, glimmering snow, the surroundings didn’t feel cold, as if normal physics didn’t apply in this world. Or perhaps being a human was a factor here too. Trying not to think too deeply about that occurrence, she focused on the task of eventually leaving this whole place.
After passing a completely boring stick she didn’t care about, the girl moved along, right before hearing a sudden crack. Looking back, she saw the same object but broken completely in half. Not feeling any ominous presence, Frisk was filled with determination and just continued her journey, not seeing any other solution for this situation.
When she turned again, the girl was greeted by probably the most grotesque individual she ever encountered in the underground, although she didn’t see much besides a few quite shy monsters. But the creature easily topped everything so far.
The male, if he could be counted as one, wore nothing else but a blue hoodie and a pair of pink, fluffy slippers. Didn’t look remotely like a human, despite having the same pairs of limbs and a head, grinning widely with his full suit of big, blunt teeth, like a famous cat from a book she once read. After closer inspection, the individual resembled a skeleton, although still having a full body, even if made entirely with bone tissue.
The slightly overweight monster looked into her eyes with his nonexistent eyeballs, which looked like deep, dark voids with tiny shimmering lights inside them. He emanated a strange aura as if he was simultaneously overly friendly and extremely dangerous. Like clowns. 
“Don’t you know about what first thing in a visit you’re supposed to say? How do you do.” The strange skeleton-like monster extended his hand, before shaking Frisk’s. A loud, farting noise echoed in the woods, luckily without releasing any foul scents. Judging by her expression, the girl wasn’t amused at all.
“Pretty funny, eh? Anyway, I’m supposed to guard this path, just like a dozen others. Don’t ask how I manage to guard half of the underworld. Anyway, I’m not really in the mood for catching any humans. Did you see any of them?” He stared deep into her soul with his mostly empty eye sockets. “Just kidding. You can call me Sans.”
While Frisk wanted to finish her journey sooner than later, her mind was filled with questions, mostly on how that skeletal person was alive. Then she remembered the crying, contradicting ghost. However, Sans was far more intriguing. Perhaps because of his joyful nature? 
“Right. I see you’re deeply concerned about how I’m alive despite not having the same parts as you. But at least you can easily find my funny bone, eh?” He suddenly went silent, as if he waited for a rimshot echoing in the distance. “But let’s stop overextending this. We both know how it’s going to end. And no, I’m not interested in your soul either. But you have something else that I just need.”
Completely shocking the little girl before him, Sans eventually removed his hoodie, completely exposing the strange ‘skin’ covering his whole body. The slightly overweight monster broke not only the laws of physics but biology as well. After all, how anyone could explain the presence of genitals, made entirely of bone structure?
“That’s right, I still have everything needed. Don’t be afraid, it’s not like I’m going to take your soul to break the barrier so all of my friends will finally escape this wretched place where we’re trapped for eternity because of you humans. Nah, I was always abstaining from politics and silly stuff like survival.”
Her heart was beating rapidly, although not because of the obvious dangers. While it felt completely illogical to be even slightly allured by Sans’ presence, Frisk was still childishly curious about the creature’s figure and how it worked. Additionally, she heard about grown-up stuff, not clearly understand it yet.
“You can touch it, I allow it. You have all the time you need. It’s not like you’re chased by a whole monster population to get your precious soul.” Frisk only sighed, getting his message a few monologues before. Her small, strangely warm hand reached the skeleton’s exposed tip, feeling its hardness. But it wasn’t as sturdy as she imagined like it was made of cartilage or even something softer.
A quiet moan escaped through San’s gigantic, mad-like grin. The girl continued with her curiosity, unsure if she was doing a good job. Especially when she didn’t get any instructions on how to use someone’s penis. She looked into voids inside his skull, looking for answers.
“Nah, dick doesn’t come with a written manual I’m afraid. But I can give you a solid ‘B’ for your efforts. But you can do better, I believe in you.” His low-pitched voice echoed inside her head but despite Sans’ words, Frisk didn’t feel threatened or insulted. It was like having that one weird friend who couldn’t stop joining even if their life depended on it.
The girl’s hand trailed down his rock-hard shaft, which seemed to be covered with a slicker surface. Although the girl wasn’t too interested in its anatomy, but rather in how it felt and what it could do. Unable to resist her urges, Frisk was deeply determined to try its taste, eventually extending her tongue in sheer curiosity.
Sans stopped joking around and finally enjoyed himself in silence, not counting a happy sigh full of relief, as if he sat down after an eternity of work. He ruffled Frisk’s neatly cut hair with his thick fingers, almost fatherly-like. He managed to not ruin the moment with popsicle puns, seeing how eagerly the human child was sucking on his long, surprisingly thick cock.
“It feels like you needed this, kid. I would say that you left those ruins in search of some ‘boning’, but let’s say that I know how to help you out. By the way, there’s more to play with down there.” Sans tried to not be too pushy, but was also more demanding, showing other places she could explore.
Indeed, just below Sans’s giant ‘bone’, there was a hard-looking sack with two spheres insides, but it resembled the same part that artisans would add while making marble statues of famous humans. Frisk massaged that place as well, feeling something lively inside as if it were actual flesh. The whole experience was getting weirder with each passing minute.
She returned in licking the entirety of his shaft, from the thick, hard-rock base and back towards the bulbous tip, which silently begged for more attention. Looking like a light-blue strawberry, she wrapped her lips around it, sucking gently like it was a pleasantly cool lollipop, basically tasteless like an ice cube.
Growing ‘friskier’ as Sans would say if he even knew her name, the chubby skeleton wanted to go further, gently pushing the girl’s head away, Being already naked without counting ridiculous pink slippers, he started undressing the young human, although even that motion wasn’t normal in his performance. A soft blue light surrounding Sans’ fingers was barely visible, but their tips were barely touching Frisk’s garments, sliding off her like they were alive.
Despite being underdeveloped, the skeleton’s ‘eyes’ were moving along the bare skin on each part of her small stature, enjoying its flat chest, slim waist, and somewhat plump thighs. Frisk felt deeply surprised at how quick Sans was in undressing her like the whole situation resembled a lewd magic trick. The skeleton would probably love such a comparison.
“I could say that you should prepare for the grand finale, but no self-respected magician would share all of their secrets.” As if he read Frisk’s mind, Sans had an answer for literally everything. The skeletal monster made a shoving motion with his hands without even grazing the child’s skin, but it was enough to make her fall on the snow, which again wasn’t causing any freezing sensations.
He kneeled before a fallen child with an exposed, hard throbbing cock between his thick thighs. Despite the lack of blood, the skeleton’s shaft seemed to be full of life and desire for Frisk before its single ‘eye’. With a few more motions, Sans managed to spread her legs wide, exposing a tight little slit. A perfect target for domination.
Sans thought about giving another monologue or at least a few words of compassion, but everything about Frisk was boiling his insides, not caused by the pure lust alone. Unable to stop himself from going further, the wide-grinned skeleton finally pushed forward, sliding a whole paradoxically meaty head past her pussy entrance.
“Everything’s good, kiddo? You didn’t scream.” Sans laughed about his words, realizing how gruesome and stupid they were, insinuating that he hoped for her painful groans. far away from the truth. Quite surprised at how brave his partner was, eventually continued by pushing his pelvis forward, exploring the child’s tight tunnel.
The whole sensation of finally penetrating a child-like Frisk was overwhelming, giving him something entirely new that he never experienced before. And it wasn’t about the flesh itself, since some monsters were built similarly to the humans. He couldn’t answer it, but maybe it was something about her soul, filled with determination.
While completely dominating her smaller and seemingly feeble body, Sans supported himself by placing his hands on each side of the snowy ground below, next to the child’s head. His piercing gaze went downwards, observing how feral his actions were, going deeper and deeper into her inexperienced pussy. It could have made him look full of himself by judging how great a job he was doing, but his actual reasons were currently unknown.
Although Frisk’s face was mostly emotionless during their entire encounter, Sans managed to finally force some emotions into her stoic expression. Her eyes were slightly more open, just like her mouth, letting out quiet moans after each powerful thrust of his sizeable pelvis. Happy that she wasn’t entirely mute, Sans continued with his conquer, wondering what else he could achieve with his skills.
“You tired me out, kiddo. I don’t remember that much of a workout in my entire life. Anyway, get on all fours. It’s still not the end, mind you. And I’m not giving you any hints, my little snack.” A hearty, low-pitched laugh echoed through the woods, while Sans held onto his round belly, apparently trying to be theatrical.
Ignoring the skeleton’s antics, Frisk listened to his demands and craved for more, unable to answer herself why she is so determined to be that monster’s fleshy cock sock. The human child raised her rump for him, exposing wet and slightly twitching nethers, ready to be ravaged once more by that impressively long and pleasantly girthy skele-dick.
Shocked at the fact that he was ready to continue actual work, Sans placed both of his enjoyably chilling hands on her butt cheeks, looking at how close the throbbing tip of his shaft was to Frisk’s begging entrance. Without delaying the inevitable, Sans pushed forward, mercilessly shoving half of the thick shaft inside the tunnel, pushing aside inner muscles.
If Sans had ears, those would be delighted by hearing Frisk’s louder moan, reverberating farther than any of the other sounds they were making. Overjoyed about experiencing new sensations, the skeleton’s actions were more irregular and impatient, as if the entire experience was deeply changing his character. Or it meant that his mask was simply slipping off.
She could feel his strong hands groping both of her plump ass cheeks as if he tried to form a piece of dough. But the lack of gentle motions made their sex only wilder, where she knew her place. Besides, Toriel already told her to befriend other monsters instead of challenging them, but perhaps Frisk took that lesson a bit too far into her heart.
Close to release, Sans felt how little strength he could muster, as if he hadn’t used half of his bones for far too long. Trying to look cool in the face of potential embarrassment, he stopped for a moment, taking a deep breath through that wide, full-of-thick grin.
“Let’s change position, kiddo. You can’t have all the fun after all. You should do your part too.” With these words, the skeleton collapsed on the snow, with his thick cock standing tall, protruding from his pearly-white abdomen. His gaze pierced her eyes once more, waiting for her actions.
Frisk felt disappointed at the skeleton for constantly changing positions, so was already determined to finish what they started. Her entrance was prepared for the next part, even if it still stung a bit when she lowered herself onto the thick shaft, pushing the thick tip past her underdeveloped pussy lips. 
With a huge grin, Sans grabbed Frisk by both sides of her thin waist, without any warning slamming her seemingly weak body like a rubber toy, up and down his cock. She didn’t look like an equal sexual partner anymore, but more like a thing he needed to get off. And that moment finally came after such a long play.
Unable to hold back his load, Sans eventually released an alarmingly large amount of thick cum deep inside her, slightly inflating her belly with his skeleton fluids. Frisk couldn’t pretend it was nothing and let out a high-pitched moan, holding onto his big, bulbous belly. Each throb of his member painfully spread apart her inner muscles even further, but even that feeling eventually stopped.
The girl collapsed, suddenly noticing how empty she was. Was it like with monster food and drinks that they didn’t work like human ones? However, it was the least of her concerts, feeling indecently exposed in a rather public-looking place. Besides, she befriended another monster so it would be obvious to just wave him goodbye and continue her journey. She couldn’t be more wrong on that.
“Where do you think you’re going, kiddo? I didn’t show you everything yet.” Frisk could swear his eye lit up in a strange, blue flame for just a second there. Or perhaps it was just her imagination. “If you want to be my friend, you have to think like me. Be like me. Or perhaps I’ll just show you.”
The girl looked even more puzzled than in her entire time inside the Ruins. Besides, she didn’t want to look like Sans, with that hoodie and silly, fuzzy slippers. But apparently, the skeleton had something entirely different in his mind, suddenly grasping Frisk’s neck from behind like she was a fussy kitten. And just like the little feline reacted, she didn’t fight back.
“Sorry, kiddo. I’m afraid you and I have to take some time to get to know each other. But hey, I’ll keep you company so you’ll not be alone. Ever.” After these words, Sans looked somewhat larger in Frisk’s eyes as if he suddenly grew in size. After lifting her way above his head, the skeleton opened his maw, proving that his mouth could move, although his grin looked even spookier that way.
The completely naked and defenseless Frisk looked straight into the void, refusing to fight and keeping a promise to not ever raise a hand at any monster. Besides, the darkness below her didn’t look even remotely as scary as the idea of eating a snail pie. Without even a chance to say anything, not like Frisk would do that, the girl was pushed further into a gigantic maw.
Her bare feet dangled past Sans’ teeth, going further down and disappearing into darkness gradually. She still wasn’t afraid when most of her body was inside the skeleton, only her head was outside, seemingly stuck. The skeleton couldn’t stop himself from chuckling and with a single push of his bony finger he shoved the last part of her body into the void.
The insides were surprisingly cozy and pleasantly cool just like the strange snow outside. She couldn’t see a thing but that fact didn’t cause a panic in her heart. It was another proof that Frisk was a strange child, having other principles than other humans, but also just acting with a different kind of logic.
Sans’ tongue showed its existence, probably unused for a long time. It slithered around the newest intruder like a ravenous, slick, and moist snake, wanting to taste every inch of human flesh. It certainly ticked when its tip licked Frisk mercilessly, even her feet or armpits. If being eaten always looked that way, then that girl could do that multiple times.
It wasn’t the end of her trip yet, feeling the insides of the skeleton’s maw moving, sparking with life. Frisk’s feet suddenly reached a tunnel, her toes going first, touching a peculiar slide. But instead of a pool filled with pleasant water, something else entirely awaited her down below. The sensation was like nothing she encountered ever before, slowly descending into a tight, moist space.
The ominous sounds attacked her ears as if each part of Sans’ body wanted to announce their existence. Frisk was further surprised, knowing well that skeletons didn’t have any bowels. But that was probably the final ace that Sans was hiding. And after rather a short ride, Frisk ended up in skeleton’s gullet.
It was probably the coziest place his body could offer to her. Somewhat warm, and dark but also acted like a good shelter from any dangers. Knowing she didn’t have to encounter any more monsters who wanted her dead. Frisk awaited her fate, filled with determination.
Sans patter his bulging, now massive belly with his usual grin, looking down at the passenger. He wasn’t great at planning, but would never waste such a great opportunity by having real human inside him. And who knows, maybe everyone else will get something from it?