Yup, this is a repost from AO3. Same me, same weird shame.

Toriel was finally finished. She confirmed the rumors one afternoon after inviting everyone to her house for tea and, of course, pie. Toriel's top secret project had been fifteen years in the making. Fifteen years since any monster had first felt the warmth of the sun. Initially, those who were close to her had been concerned. After all, many monsters were having a hard time adjusting. Many suspected at first that was why she spent so much time back in the ruins. But over the years, it became clear that whatever she was doing, her time was being well spent, as she always came back more cheery and eager about whatever else needed to be done around the school or in the community. Eventually everyone came to accept the occasional long hour spent working in the mountain as just another habit of hers.

Now, though, it was finished, whatever it was.

Setting down her teacup, Alphys was the first to ask, "So… what IS it, though?"

Before Toriel could answer, Papyrus, covered in crumbs, rose out of his wing chair.

"YES! WHAT INDEED! WAIT. I, THE GREAT PAPYRUS, WILL VENTURE A GUESS. HMM. AH! OF COURSE! IT'S SO SIMPLE! YOU HAVE BEEN STRATEGIZING A WAY TO REINSTATE THE ROYAL GUARD! HONESTLY, TORIEL, HAD YOU TOLD ME I WOULD HAVE GLADLY LENT YOU MY EXPERT ASSISTANCE IN THIS MATTER! IN FACT, WE WOULD BE DONE BY NOW AS I HAVE SUCH A MIND FOR STRATEGY. BUT. IT IS NOT TOO LATE TO ASK ME TO BE CAPTAIN. IF THAT WAS SOMETHING YOU WERE WORRIED ABOUT."

Undyne glared daggers at him and he promptly sat down.

"Well-no," said Toriel. "Now, dear, we've been over this so many times before, and there's just no need for a royal guard anymore. Thank you for your offer, though. It was very sweet and generous of you, as always. But as I was saying, when you're all through eating, I thought we could take a quick hike through town to the mountain and I'll show you all what it is I've been working on."

Toriel beamed at the various monsters now chattering away in her living room. You, too, were relieved everyone had been able to make it today. It wasn't too often anymore you got to see all your friends in the same place at once, and you knew it especially meant a great deal to Toriel.

As everyone gathered their things and got ready to leave for the mountain, Alphys came up beside you, fidgeting.

"Listen, um… I don't really like surprises, you know? I mean, I… I just like to know beforehand how I'm supposed to react, and I was hoping y-you knew? What her project was… since she raised you, I mean."

"Oh! No, I'm just as much in the dark about it as everyone else. But try not to worry about it, ok? You're among friends."

Alphys smiled sheepishly. "You're probably right. I just don't want to mess up Toriel's moment and say the wrong thing but I-"

The doorbell rang. Not an unusual occurrence, as popular as Toriel was in the monster community but… all the people who usually came to see her were here. You counted. Alphys and Undyne, Papyrus, Asgore was somewhere keeping to himself, Mettaton and Napstablook, Muffet had gone into the kitchen to pour herself one last quick cup of tea, there were at least four Temmies, and that... should have been everyone. Maybe Toriel had invited someone from the school.

She practically jumped and, before answering the door, she looked at you and grinned so brightly you knew she knew something you didn't.

And so it was. Winded and slack-jawed, you took in the surprising sight of the new arrival. That is-of course she'd invited him, you just never expected he'd actually come.

Beaming, Toriel drew him into one of her signature warm and cozy as fuck hugs.

"BROTHER. YOU DID NOT TELL ME YOU WERE COMING TO THIS AUSPICIOUS GATHERING. I AM HURT BUT I, THE GREAT PAPYRUS, WILL GRACIOUSLY FORGIVE YOU IF YOU WILL GIVE YOUR BROTHER A WELCOME HOME HUG."

Sans. Wasn't he supposed to be in… ummm… The last postcard he'd sent you was from Helsinki. Or was it Jakarta? But that had been over a month ago. Guilt stung you and you resolved to keep better tabs on him in the future.

Everyone crooned over Sans' return, even Undyne, in her way. You hung back. The last time he'd been in town, you had-well, you had… misjudged a certain situation and left things a bit awkward. But that was a little over a year ago. Surely by now he'd forgotten and all would be well again. You hoped so, anyway, as you drew close for your turn to hug him.

His eyes shifted as he gently, awkwardly patted your back. It was over so briefly it barely registered but for the fake-ass grin he had plastered on his face.

Nope, still awkward. Ok.

"Hey, Frisk. Good to see ya, kid!" he said, a touch too loudly.

"Hey, Sans. It's good to see you, too," you half-mumbled, smiling painfully as you turned to go pretend to be busy in the kitchen.

You could handle this. This was just some standard, everyday, haha-whoops-I-drunkenly-tried-to-kiss-you-the-last-time-I-saw-you awkwardness, and you would deal with it. Today, you could just avoid Sans except when necessary and nothing would have to be weird or uncomfortable for anyone else. Actually, you probably wouldn't even have to do any work to avoid him. If that hug was any indication, he'd probably do a fine job of avoiding you, as well. Toriel's grand unveiling of her project filled you with Determination.

"Is everyone ready?" called Toriel.

You would walk to the mountain with Asgore, you decided as everyone filed out the door and paired off. Asgore was a safe choice.

Asgore had other ideas. He surged ahead to the front of the party, to walk with Napstablook behind Toriel and Muffet. He did not seem remotely interested in his ghostly walking buddy, though.

"He's still trying that?" murmured a low voice next to you. You hadn't even seen him draw near. "I thought my brother and I were the only two boneheads around here."

You prickled a bit, because honestly, what did you just say about avoiding him? Apparently he hadn't gotten the memo. But if he was really that uncomfortable around you, then why did he immediately seek you out? Maybe you'd misjudged him again. If only he wasn't so hard to read.

"Two boneheads? Interesting, because for the last... mmm... seven years I've only counted one."

That came out a bit harsher than you'd intended.

"Haha, woah, are you trying to guilt trip me right now? Y'know, it's okay to admit that you missed your uncle Sans. Also, you missed the part where you say, 'Oh, Sans! You and your brother aren't boneheads!'"

His impression of you was a truly unfortunate creaking falsetto.

"I would've, but actually I was still talking about Asgore."

Sans chuckled.

"Oh and Sans? How about you literally never call yourself my uncle ever again?"

"Yeah, I think I can live with that request. Never really thought of myself that way, no reason to start now." He looked at you as if he was trying to work out a problem. You kept your gaze fixed straight ahead on the leafy path through the trees.

"I did miss you, though." Don't blush. Don't blush.

You blushed.

"I mean. We all did. Of course."

"Yeah? Hmmm..." he said noncommittally.

The two of you walked a moment in silence. You were beginning to lag behind the rest of the group, Sans' lazy stride not getting you anywhere fast.

"Ok," he said out of the blue after a moment of quiet reflection, "it's my turn now, to send you on a guilt trip."

The contents of your stomach, and your mood, soured.

"So. Why is it, that even though I get daily phone calls from my brother, and let me tell you, that does not come cheap long-distance, and Alphys constantly messages me on Facebook, and Toriel sends me handwritten letters and way too many baked goods no matter how many times I change my address, and-do you know even Undyne checks in on me from time to time? I guess what I'm trying to say is,"

His voice was outwardly cheery and he wore his signature grin but the lights in his eyes had gone out.

"If you're going to tell me you missed me and act like we're still friends, maybe you'd better explain what you meant by giving me the silent treatment this past year."

Oh, god. He wanted to talk about this now?

"Honestly?" you managed to get out, "I um, didn't think you'd want to hear from me after the way we left, uh... things. After the way I messed things up and you left."

The lights reappeared in his eyes as a slow smile spread across his face. "Things, huh? What things," his voice dropped, "do you think you messed up?"

You looked away. "Now you're just teasing me, and it's very mean of you, Sans, and I-"

"What things, Frisk? I'm curious."

"Y-you're gonna make me say it? Really? Ok, shit, I'm sorry I drunkenly kissed you at Alphys' hatch day party last year. I mean um, that is, I'm sorry I tried to."

Sans stopped in his tracks.

"You are?"

"I- Yeah, I must have misread the situation. I was drunk and you were so... Well, that doesn't matter. I thought maybe you had finally started to see me as an adult and I hoped that... Umm... But clearly we were not on the same page that night and I'm really, really sorry."

You had halted when Sans did, but now your throat had gotten tight and your voice had grown shaky sometime during the last sentence. Like hell were you going to cry about this complete nonsense, so you decided it was best to stop babbling and start walking. The group had kept moving forward and were now out of sight.

Before you had even taken a second step, bony fingers closed around your wrist. His grip was firm, not a vice, but it held you there all the same. You turned toward him and for once, he wasn't indecipherable Sans. His concern was as clear in his expression as the tip of Mt. Ebott over the treetops.

"So that's why I haven't heard from you? Because you didn't think I wanted to-"

He stopped himself short.

Grinned suddenly, like a punchline clicking into place.

"But you DID miss me, right?"

"I-yes."

His 'crazy eye,' the one that used to scare you, began to glow bright blue as he pulled you closer. Your heart did a rimshot in your chest.

"Missed me?" he asked again, his tone, leading.

"What? Yes, I just told you, what are you-"

"Now ya gotta kiss me."

Sans' face was so close to yours, a couple of centimeters or less. Everything was blurry and you couldn't tell if that was from the sheer shock of finding your body pressed up against his, or just the natural biological fact that people often don't see clearly what is right in front of their nose.

Your face, you knew, was likely red from your hairline down past your collar. Wasn't this precisely what you'd been waiting for? But… no. He couldn't just go from forcing your hand into embarrassment to expecting you to want to kiss him. Even if you did want to kiss him, but that was really not the point. Sans had always gone from 0-100 at a moment's notice when you least expected it. But regardless of the color in your cheeks, and the fact that in spite of yourself you were leaning forward, and your rising heart rate, and the fact that even though it was late autumn and you were wearing a thick sweater, you were extremely warm-regardless of all of those things, you needed to disabuse him of the notion that you would simply follow his lead and dance to his ever-changing tune.

You narrowed your eyes.

"Where's the whoopie cushion, Sans? Isn't that how you usually end a joke?"

That was probably too mean for the situation at hand. Sans actually looked a bit hurt when you separated yourself from him. He recovered quickly, though, as he always had from hecklers and pun-hating brothers and confused, flustered 25-year-olds alike.

"First off, the whoopie cushion IS the joke, and second, actually now I've got an app on my phone that does a rimshot when I press a button, and-"

"AHEM." Undyne stood, glowering at the you with arms crossed. You had no idea how long she'd been there. Was she just exceptionally sneaky for a fish monster on land or had you really been that oblivious to her approach?

Alphys came trotting up beside her, gasping for breath. "Hch, Tori… el… sent us, she… hch- um, she- whoo, hang on."

"She won't cut the ribbon unless you losers catch up with the rest of us to see it. So are you coming or d'you want me to tell her you're busy?" Undyne wiggled her fins suggestively.

"Ohmygod did they-"

"-SHHHT."

"HA! You owe me a-"

"HSSSST."

"Oh! Right! No! I meant that… you owe me an explanation for running off ahead of me. Which you actually do."

The pair had already turned back to the trail.

"I'm sorry, dear. You know how I get when I'm on a mission."

Undyne clasped Alphys' hand in hers, you and Sans and your tardiness apparently already forgotten. Why couldn't things just be easy like that?

Not daring to risk Undyne's impatience a second time, you and Sans followed close behind, silent.

Sans took his phone out of his jacket pocket, typed something into it, then put it back. He looked at you expectantly and a moment later, yours buzzed. Your eyebrows snapped together.

"What, am I back in high school now?" you muttered, making a show of pulling out your phone.

Sans: I'll bet you an appetizer from Grillby II's that you still want to kiss me.

You cast your eyes up to the heavens and heaved the most long-suffering of sighs.

You: What kind of a bet is that? If I won, I'd get free nachos, but IF you won, you'd get nothing because you don't eat real food.

Sans: That's a decent point, but if I won it'd mean you DO want to kiss me. Also, and more importantly, it would mean I was right ;)

You glanced at him out of your peripherals and he actually winked at you, the fucker. You shoved your phone down in your pocket and picked up your pace a bit. Your phone buzzed against your thigh in rapid succession.

Sans: Hey

Sans: Hey

Sans: Hiya

Sans: Hey

Sans: Guten tag

Sans: Hey

You: WHAT.

Sans: Knock knock.

You: Fuck you. Who's there?

Sans: Anita.

You: Pretty sure I've heard this one before, Sans. Anita who?

Sans: Anita talk about some stuff with you.

Another sigh from you. If you kept it up, someone would probably think you had caught feelings.

You: I just need some time to think. But we'll talk, just… later, ok?

You put your phone away for good when Sans nodded at you. It was only a minute or two before you finally caught up with the rest of the group. All of them stared at you before turning to watch Toriel gleefully cut the ribbon. She ushered everyone in with delight, but saved a special stern look just for you and Sans.

What a disaster.

At the end of the first corridor, Toriel gathered everyone around in a somewhat tight huddle, as the corridor wasn't meant to accommodate quite so many monsters at once. Anytime Asgore shifted a muscle, the entire crowd jostled, and you found your side pressed squarely against Sans'.

"Thank you all again for coming today, because it is my pleasure to welcome you to the unofficial first opening of…"

Toriel beamed in her dramatic pause.

"The First Museum of Monster History!"

"What an excellent name! Much better than I would have come up with!" said Asgore, clapping and chuckling a little too heartily.

Toriel scrunched her face up a bit.

"Yes, well. It's not set in stone yet, I haven't ordered the signs. I might call it the… Mount Ebott Museum of Monster History. Or the New Museum of Monster History. Anyway, um. It's through here, everybody! Please enjoy history responsibly!"

Everyone cheered. It was for Toriel, whether or not they actually planned to "enjoy history responsibly".

After the slight bottleneck through the main door, everyone scattered to find whatever interested them. Not with a small amount of relief, you watched Sans and Papyrus head off together. Good. Now you had some time alone to... gaze at this rock.

You tried to read the plaque next to it but you couldn't seem to focus on any words past, "This keystone was cemented into the Grand Northern Archway during the first gathering of the... This keystone was cemented into the..."

"Hmm, neat rock," said Alphys. You didn't think she had read the plaque either. "Hey, would you maybe want to come over for dinner with us later? Netflix just bought Robocop 5 and Undyne is dead set on "hate-watching" it. I think the real reason, though, is that-" Alphys whipped her head around to check nobody was listening and dropped her voice to a giddy whisper. "They show Mettaton's butt."

She giggled.

Dinner tonight? Hmm, that would keep you out of trouble.

"Sure, I'll be there. What time?"

"How about seven-thirty?"

"Great, I'll see you then."

Alphys left the room. Good, you thought. Things were already returning to normal.

The rooms of the museum, you noticed, were arranged by topic. The first room had been about the war, the placement of the barrier, and the ruins themselves, the foundation of old Home. The next room was dedicated to early underground art, culture, and daily life, and you noticed the plaques' language seemed almost wistful. Not so in the third room. Toriel had pulled no punches, making her opinion of Asgore's actions perfectly clear, just as she always had. You found him in the next room sitting on a stone bench, head hanging. You squeezed his shoulder, gave him a sad smile, and left him to his regrets.
This room was one that somewhat concerned you. The sign said, "The Last Age of the Underground: Contemporary Life in A Time of Unease and Paranoia".

It was in this room that the bulk of the group lingered. They were all remembering. Uneasy and paranoid their time may have been, but there was nevertheless a general feeling of homesickness. Many held back tears as they stared through exhibits that transported them through time back to their old homes and past selves.

You waded through wobbling smiles to the next, and penultimate, room, titled "The Semi-Permeable Membrane: Dispelling Ancient Rumors Through Human Archaeology".

You were baffled. This was all... human things. You hadn't thought many humans had ever come to Mt. Ebott. The introductory plaque on the wall immediately contradicted your thoughts.

"Despite rumors that humans never returned from Mt. Ebott, many humans actually visited the mountain and left unharmed, as humans tend to do with most mountains, even the ones purported to be dangerous. Even though only a handful of humans ever actually did fall to the Underground, it was nevertheless the case that numerous campers and naturalists often found their belongings missing. In this room are some such items that fell to us."

"Hey, sweetheart, do you... Do you like it?"

Toriel stood behind you, face full of eager hope.

"Aw, mom, it's really-it truly is wonderful. I'm so proud of you. Really, you've done an amazing job."

She gathered you into a hug.

"But how did you do it? I mean, these glass cabinets, these really professional looking signs, the sheer amount of renovation?"

Toriel shrugged.

"I got a grant a few years back from the embassy. That sped things up quite a bit."

Like it was nothing.

"But mom, I work at the embassy. Surely I would have heard something?"

She shrugged again.

"Hmm. Weird." Was she dismissing you? "Anyway, why were you and Sans so far behind everyone else?"

And now she was turning the magnifier onto you. A classic evasive maneuver. Had she learned it from you or you from her?

You stepped away. Her teacher eyebrow went all the way up.

"Uh, it's a funny story actually, remind me to tell you all about it later!"

You pretended to be suddenly really interested in a busted up Walkman.

"Ha! Hey, this thing has a Seal CD in it! Oh, it's broken, too, though."

"Uh huh," said Toriel.

You hoped she would show you mercy and drop it, at least for now. You scanned the rest of the room in hopes of finding another distraction-wait, was that a-no, it couldn't be-nope, that was decidedly and unmistakably a neon blue phallus.

Oh, no.

"Uhhhhhhh, mom?"

She followed your gaze.

"Oh! Curious little thing, isn't it? Come look!"

Horrified, you followed your mother to the exhibit in question.

"You know," she said, "when I first saw it I thought it somewhat resembled a crude miniature of-" she glanced behind her. "Well, anyway, now I think it must be some kind of toy!"

You choked.

"Oh! And look what else it does!"

She unlocked the case and removed it, turning it over and switching it on.

"See? It buzzes AND it lights up!"

She handed it to you, so proud of her interesting find.

"Huh." was all you could say.

She bit her lip.

"Oh dear, I'd better go back, I think I just heard crying. I knew I shouldn't have left anyone alone in that room."

She kissed you on the cheek and left you standing holding a vibrating, blue, glowing cock in your hand.

This would simply not do.