A/N: Warnings first. This is technically underage. Sorry, couldn't get around that. It's a fact. Frisk is 16 in this one-shot. I promise nothing sketchy is in here. It's mostly just fluff and Sans's thoughts. Loyal followers know I don't go for squicky stuff.

Honestly this feels more like ramblings than anything. And it's maybe a little OOC? It's hard to tell. It's two in the morning. Anyway have some cuteness and I hope you enjoy.

For Sans, it wasn't a matter of "falling in love". He wasn't even sure he could classify it as love. He loved his brother, he loved Toriel, he loved Grillby, and he especially loved all of his friends. They had been there for him even when things got rough. Their relationships had lasted through thick and thin. There had been fun times and hard times. Really Hard Times. But yet their love had persisted. And isn't that what love was supposed to do? Persist? So Sans loved his friends and family.

But his feelings for Frisk had always been complicated. There was no one way to describe how he felt about them. The most that he could say was that he loved the kid with a passion...but he wasn't sure how to describe that passion. It was stronger than his love for his other friends...practically on par with his love for Papyrus...but somehow didn't fit into the same category. In many ways he obsessed over the human. When they weren't with him, he would think about them throughout the day. When they were with him, he felt content and happy.

And yet there was a part of him that hated Frisk. It was a part he never expected to go away. It was a part that if he so much as poked at it, it would fill him with bitter feelings and hatred. And the only person he could really direct it at was Frisk. Because it was their fault. He suspected now that he was older that it was in response to his LOVE. He couldn't decrease his LOVE now that he had it, so it came out in the form of bitter resentment. Even though he didn't blame Frisk for what they did because it was Chara's fault. But...

Anyway. Sans wasn't one to think on these things. He didn't care about what he was feeling. From personal experience he had realized that it was just better to ignore these things. It meant he would have to introspect too much and that was just a hassle. And could make him depressed. He would much rather sleep or just live life in the moment. But in the past couple of years he had been on the surface (and time was marching forward finally), he had time to think about these things. Papyrus didn't need as much support as he used to, things were generally right with the world, and Frisk...

Well. Sans was having more and more difficulty not watching them.

Frisk was a high schooler now. He couldn't even really call them a "kid" anymore when they'd had their sweet sixteen not too long ago. They were maturing and handling the world in a way that was admirable for someone their age. But who wouldn't expect that from someone who had saved the entire monster race when they were just twelve? Frisk was older and Sans couldn't call them a kid anymore. And that was a problem. Because they were still young, but they weren't a kid, and Sans was finding them more and more attractive.

Sans didn't date. It wasn't something that he did. It wasn't that he hadn't found people that had interested him before...it was just that most of the time they wanted something from that relationship that Sans, for the most part, didn't feel like giving. Sex, that is. No need to go into the gory details, but things just didn't work that way with him. The monsters that he had been together with (and by together, he meant snuggly. Not dating) had understood a lot better than the humans he had flirted with. But most of those monsters and humans had needs that Sans just didn't have so things lost the spark fairly quickly.

So Sans didn't like to date. It was a hassle, usually ended in him a little more heartbroken than he had expected, and frankly he just didn't have the motivation to pursue anything. It exhausted him trying to keep potential lovers happy. Frankly he could live off the vicarious joy of his friends hooking up with other people. Alphys and Undyne had been together for so long now that it gave Sans hope. Sue him if he was a little bit of a romantic at heart. He and Papyrus had a lot more in common than a lot of people thought. The two brothers were content with just having each other.

But then things started to get tricky with Frisk. It wasn't anything that Frisk did -no, in fact Frisk and Sans had a great relationship with each other. An "open" relationship, according to the town, considering the two of them had been "dating" since Frisk was thirteen- but rather it was Sans recognizing strange reactions in himself. He had first noticed it when Frisk had gone on that cute little date with Lansot years ago. The second time he had noticed it was when Frisk had accidentally kissed him. But it wasn't until recently that his reactions became more obvious.

Frisk was dating.

Actually dating.

And Sans...Sans didn't like it. At all.

He couldn't really explain it. Lansot was a great person. They were open, friendly, adored Papyrus, was respectful of Frisk's boundaries, and was attentive towards Frisk's needs, if Frisk was telling Sans the truth. But Sans didn't like them actually dating. He found himself occasionally peeking in on dates that he shouldn't have been looking in on, and also found himself staring at some of the cute couple photos that Frisk and Lansot took together. It was hateful, he knew, but he couldn't help it. Lansot would never be able to understand Frisk the way they needed to be understood. Frisk was a complex person with complex feelings. And the only one thus far that had been able to handle all of them and to actually understand was Sans himself.

And now, Sans wasn't stupid. He recognized this disgusting slop of negative emotions bubbling in his gut. He was jealous, plain and simple. And he shouldn't be. He was Frisk's best friend and Frisk was his best friend. It wasn't like he was being replaced. Frisk had tons of friends and cared about every single one of them. But Sans, in a way, had always been their most important friend. Their closest friend. The one they relied on emotionally. Yes, over the years, they had opened up more to their other friends, but Sans had always been the first. And this was fucked up thinking. Sans loved the human. He'd always loved the human. He had recognized and accepted this as a part of his life.

But he was realizing now that he was actually in love with the human.

And that scared him for many reasons. For one thing, he hadn't even noticed. He had been emotionally dependent on Frisk, but when did that emotionally dependency turn into something more natural rather than frantic? Another factor: Frisk was still underage. He had told himself in the past that it was okay to say they were dating because nothing had really been happening between them. Romantically, sexually, or anything like that. But now...now Sans knew he had feelings. Actual feelings that officially crossed a line. So that was scary. But the final reason was that he needed to now deal with the repercussions of these feelings.

Frisk didn't love Sans in that way. Sans would've noticed by now if Frisk thought of him that way. Or would he? Fuck, he couldn't even recognize it in himself. But he had seen how others looked at him when they wanted to be with him. So shouldn't he be able to recognize that in Frisk? Yes, he certainly thought so. Which led him back to his original conclusion that Frisk didn't love Sans that way. The final proof was the fact that they were dating other people. Sans hadn't even been an option in their eyes.

And that...hurt a lot more than it should.

Sans stared at the television without even watching it. Papyrus was at his job today and had yet to return home for the evening, and Sans had taken a personal day. Which, in retrospect, was probably a bad idea. He had gone into this personal day with the intention of figuring out why he was being an idiot around his best friend, and unfortunately he had figured it out. Way to open a can of worms. Now he was here on the couch and, rather than enjoying a free day, was moping about his non-existent love life. Fucking fantastic. Like he was some human on a television drama.

This is why he didn't do the dating thing. It would end eventually. Frisk was a healthy teenager so they probably had those urges. They hadn't talked about it. Sex was a stupid thing to him. He and Frisk had actually sat down and watched (human) porn together for the shits and giggles. And it had been pretty gross. And hilarious. But Frisk, as far as Sans could remember, hadn't reacted. But that didn't mean anything. He didn't personally know the signs of human arousal anyway. And porn didn't count. That stuff was all overly dramatic anyway.

And if Frisk had those urges and they were dating Sans...things would just fall flat. He'd seen too many shows to know that humans as a species just didn't seem to know how to function without orgasms. Everything in their society seemed to come down to sex one way or another. Frisk was special, but he doubted that on a biological level that they were much different. So Sans was saving their friendship by not trying to pursue anything.

Not that there was anything to pursue because Frisk didn't like him that way. They were dating Lansot.

Sans groaned at his own stupidity. He couldn't get this shit out of his head. He was going in circles thinking of 'what-ifs' and such. He was discouraging himself from something that wasn't even going to happen.

But he and Frisk would be good together, he knew. Yes the sex thing may be a problem, but Frisk would already know going into the relationship that he wasn't interested in that stuff. They would never try to make a sexual relationship happen. Hell, they had seen enough porn with him that they could take care of their own needs. He didn't mind. He just...

God, what the fuck did he even want from Frisk? He wanted them, but he already had them. In almost every way he and Frisk were already a couple. They had been for years. The only thing had been the false label on it. But the image of Frisk cuddling up with Lansot wouldn't leave his head. Going on dates, cuddling, kissing...he wanted those things. Even if he didn't have lips. The few kisses he had received before had been...nice. More than nice. He wanted to actually have the chance to explore the feeling of Frisk's lips on him. To memorize it like he had already memorized how they felt in his arms.

He sat up on the couch. Shit...he was really in deep. Goddammit. Fuck. Fuck! He slipped off of the couch and pulled on his slippers before heading out the door. He locked it behind him and stuffed his hands into his shorts pockets before beginning to walk. He needed to clear his head some. This wallowing? It would drive him crazy. He should have left well-enough alone. This is what happened when he explored his own emotions. He got screwed over.

Sans returned all of the locals' greetings as he entered New Grillby's and sat in his usual seat. "heya, grillby. get an order of burg over here." Grillby nodded and headed into the back for Sans's burger. Sans placed his cheek in his hand and scoped out the bar. It was still early in the evening, but there were already a number of customers there. Good-looking people that Sans wouldn't mind getting know. But he couldn't even work himself up to it. He sighed and turned back around as Grillby set down his burger in front of him. "thanks."

Grillby picked up a glass to clean and stared at Sans. The flames crackled with curiosity, but Grillby had never been one to push another to talk. He was there to listen and he was great at it. Sans, though, wasn't prepared to talk to him about it. There were only two people he could consider confessing these feelings to, and one of them was the problem. Papyrus may be a good choice, but he wasn't certain that his brother wouldn't try to play matchmaker.

Sans grabbed the ketchup and squirted some onto the burger before beginning to drink the rest. Grillby placed a new bottle onto the counter next to the mustard. Mustard may be a good shock to his senses. He'll try that next. Grillby gave him a disapproving look that Sans ignored. Sans took a bite of his burger before leaning forward some in his seat. "hey grillby, d'ya think me n' frisk are dating?"

Grillby didn't answer for a long moment before he nodded. He also shrugged.

"you 'n everyone else." Sans agreed. He took another bite of his burger. "s'not true though. me 'n frisk. they're with that little monster kid that likes to hang out front."

If Grillby was surprised, he didn't show it.

"so if we're not dating, i should clear things up, right? just so people stop saying we're together. save everyone a hassle. s'great idea, right?"

Grillby readjusted his glasses.

"yeah," Sans nodded and finished off his burger in two more bites, "you're right. the joke ended a long time ago. better to end it now." He slid off of his stool. "put it on my tab, alright?"

But Grillby wasn't looking at him anymore. He was looking at the door, and when Sans heard everyone greeting Frisk, he mentally winced. He hadn't expected to see them today. He was honestly just gonna text them and tell them that they could end the dating farce now. He spun around and strolled casually up to Frisk. "sup, pal. here to eat?"

Frisk shrugged and pointed at Sans.

"i was just heading out. took a day off, see, and i got sleeping to catch up on."

Frisk held up the backpack they were holding. "Help?" They asked. Ah, science homework. The bane of Frisk's existence. The human wasn't half-bad at it, they just needed it to be taught to them by someone who did science for a living. Namely Sans or Alphys. Tori wasn't a bad teacher either, but sometimes it bothered Frisk to have their mother have to teach them these things.

"sure." He agreed. He doubted their work was very difficult and it would be a good distraction. Sans and Frisk both waved to everyone before they exited the bar and took a shortcut back to Sans's house. Papyrus still wasn't home. Sans opened the door and the two entered. Frisk took their shoes off at the doorway, but Sans didn't even care. They took to the kitchen where Frisk started digging out their books. Sans watched them. Their hair was up today. It was longer than usual, reaching past their shoulders, and it wouldn't be long before Frisk wanted to get a haircut. They liked their hair long-ish but not this long. They wore a ribbon in their hair -most likely Asgore's handiwork- but it didn't match their tee shirt and shorts combination. Frisk wasn't the best dresser. Especially since their shorts were polka dotted. It's amazing how many kid clothes the short human could still fit into. Even though they were a little taller than Sans himself now.

Frisk scooted their chair closer to Sans and the two of them leaned over the science textbook. Frisk pointed out the problems they had to work on, but Sans found himself embarrassingly distracted. Frisk's hair smelled differently. More masculine than the usual flowery scent they used to shower with. He must have lost control over his mouth temporarily because before he knew it, he was pointing this out to Frisk.

Frisk tugged at the loose bangs on their forehead and stared at them. "...Wanted to try something different." They admitted. They looked at Sans. "Bad?"

"s'weird." Sans admitted. "not used to it."

"Bad?" Frisk repeated.

Sans shook his head and swallowed. He kind of preferred the flowery scent. It suited the human. The smell of flowers reminded him of that strange summer scent they had carried with them for days after they had escaped from the underground. "just...weird." He muttered stupidly.

Frisk touched his arm and drew his attention to them. Oh great, they had noticed he was being weird. He hadn't even tried to stop it, and Frisk was way too good at reading him. Fuck. Well, best to get it over with, right? "so, uh, you're with that kid lansot now, right?"

Frisk teeter-tottered their hand back and forth and shrugged. Wait, what the heck was that supposed to mean? Frisk shrugged. "Sort of." They said. Sans waited for an explanation. "Casual dating. We're both...trying it out. It's nothing official."

"so what, like us?"

"Less official."

That...what? "less official than fake?"

Frisk paused and their face did something complicated. They watched Sans for a few moments before looking down at their hands. Their fingers fiddled with the paper in their textbook. Sans continued to wait. Frisk finally looked at Sans from under their eyelids, almost nervously. "...Fake?" They asked.

Now it was Sans's turn to freeze up. He chuckled a little out of habit. "uh...yeah. remember? christmas? the first one we all had together?"

"...Oh."

An awkward silence fell over both of them. Sans didn't think that things had ever been this tense between the two of them. At least, not in this way. This was uncomfortable, but there was a tiny part of him that was beginning to hope. He tried to smother it quickly, but the confusion only allowed it to take hold. Why was Frisk suddenly so disappointed?

Why was his life suddenly a romcom movie?

"...er..." Someone had to bring it up. Sans usually would let shit like this pass, but he was clearly out of his mind today. Might as well go full throttle. It usually worked out well enough for Papyrus. "...frisk...do you want to actually be dating?"

Frisk shifted uncomfortably and refused to meet Sans's gaze. Their cheeks were pink but he wasn't sure if that was mortification or embarrassment at being caught out. They continued to be silent until he noticed a change go over them. Their determination. Frisk sat up a little straighter and faced Sans head-on just as Asgore and Undyne had always taught them. "If I said yes, what would you do?"

Sans's grin was strained. "it doesn't matter what i want. you're still a kid."

"I'm not a kid." They said and god, Sans was well-aware of this. Their face was the face of an adult. They hadn't been a child in a long time. "But...I understand." They deflated a little. "Too young...or not interested?"

"...listen, buddy, even if...this happened...what would you even want out of it? i can't give you anything that you don't already have."

"You." They responded. "I have everything from you...but you."

Sans chuckled a little. "frisk, you've had me for years now." Frisk seemed surprised. "annnnnd judging by your face, neither of us seemed to have caught that."

Frisk stared at Sans. Sans wiped at his face with his hand. Weren't they supposed to be doing science homework? The silence had gone on long enough that he was just about to suggest that when Frisk shifted forward in their seat. He watched them as they pulled their chair up to his and they leaned over the rest of the way to press their lips to his teeth.

Sans's eyes widened and he fully expected one or both of them to jump away, but Frisk just pressed in deeper until their arms were wrapping around his neck. Despite the slight awkwardness to it, he could still feel the emotion behind the gesture. And goddamn this kid for always being able to get to him no matter what. His hand came up and found their cheek, and their head automatically tilted into it. Sans could almost feel his soul jump.

His eyes fell closed as his other hand found the human's hips. He tugged very lightly -a suggestion- and Frisk followed through. The chair creaked under their combined weight as Frisk settled into his lap. They were taller now. Sans's finger squeezed around their hipbone as his other hand slid up to cup the back of their head and tilt it downwards. The kiss broke and their foreheads touched each other. Now Sans was certain the pink in Frisk's cheeks were from affection than anything else.

"...i can't kiss you back." He said, and was surprised to find his voice on the breathy side. Well that was embarrassing. Frisk was staring into his eyes, but their own eyes kept darting to his mouth.

"...I don't mind."

"i can't be everything that you want."

"I don't care."

"you should."

"Stop trying tibia mature adult." Frisk scolded playfully, and Sans grinned. He liked this, the intimate air between them. It was unexplored territory. It felt like a good next step for their relationship. But he couldn't focus well like this. There were important thing they needed to talk about. He had tibia mature adult about this.

"frisk." He warned.

Frisk pulled back but didn't get off of his lap yet. "...I can wait, if you're willing. We're already...been dating for a long time. We...don't really have to do much different. And...in a way, I'm a lot older than I am physically. Because of the timelines."

They were excuses, Sans knew. But the kid also had a good point. At this point, he wasn't sure why he was fighting it. He preferred to just go with the flow. People have complained about their relationship before, but things were pure between them. He certainly wasn't gonna try anything weird.

"...thing's will be different though, pal." He pointed out, looking down at where his one hand had rebelled and was still holding onto Frisk's hip. His thumb, being particularly rebellious, was stroking the tiny sliver of exposed skin there. It was soft, dry, and warm. "besides, uh, what about lansot?"

Frisk tilted their head in question. "Monogamy?"

Sans shrugged. "do what you want. we're not exclusive until you're eighteen."

Frisk looked a little put out by that, but didn't argue. Instead, they leaned down and pressed a kiss to Sans's cheek. The promise was sealed. He closed his eyes and pressed his own form of a kiss to their cheek before resting his head against their clavicle. He could tell them right here and now the extent of his feelings, but he decided against it. Some things just didn't need to be said. Besides, this day had been a roller coaster and he was exhausted. A nap was in order. His eye caught the textbook waiting patiently. He supposed it was about time they start on that before it got too late. And if that meant moving first to the couch so he could hold Frisk in his lap while they worked? That was just fine.