Sans hurriedly ushered the human child inside his house, loudly shutting the door behind him.

"SANS?" Papyrus called from the kitchen. "WHAT IS-?...OH...OHHHH NOOOO…" Papyrus looked back and forth at the child and his brother, unsure of what to do. "WELL, UM. IT APPEARS THAT YOU HAVE "CAPTURED" A HUMAN CHILD."

"things aren't always what they appear to be, paps." The taller skeleton gave the smaller one a look.

"THAT CLEARLY ISN'T THE CASE HERE, SANS. WHAT ARE WE SUPPOSED TO DO? WE CAN'T JUST KEEP THEM HERE!"

"well, bro. i think the answer is pretty obvious." Sans turned to the child. "up for an adventure?"

XXXXXX

Making their way through waterfall would have been much easier if they didn't have spears being hurled at them. Sans ran at full speed, child over his shoulder. Papyrus blocked as many spears as he could with his own magical attacks.

"UNDYNE, PLEASE!" he pleaded. "LET US GO!"

"I will not let you protect a human!" The fish woman bellowed. "You are all standing in the way of everyone's hopes and dreams! Now, allow me to take their soul to Asgore!"

"I WILL NOT!" Papyrus winced, an arrow having grazed his arm. "I REFUSE!"

"Tch. I don't want to hurt you, Papyrus. But you're not giving me a choice."

The fight continued.

Sans and the child were long gone.

XXXXXX

"SANS, I HAVE BEEN FINE FOR HOURS. PLEASE STOP ASKING ME."

"i know, paps, but that fight with undyne left you pretty weakened, and we don't have any food to heal you with. i can't help but worry." Sans glanced up at his brother. "did she have to be so brutal?"

"YOU KNOW HOW SHE IS," Papyrus grunted. "IT'S IN HER NATURE TO BE FEROCIOUS IN BATTLE. BESIDES, SHE WAS ONLY DOING WHAT SHE THOUGHT WAS RIGHT."

"unfortunately," the shorter grumbled. He paused when the child tapped his shoulder. "hm? what is it? want me to put you down?" They nodded. "there ya go, kiddo." Suddenly, Papyrus froze, letting out a large groan. "Uh, Paps?"

"I JUST REALIZED THAT WE NEVER ASKED THEIR NAME!"

"huh. you're right. "

"ALL THIS TIME, SANS, AND NEITHER OF THOUGHT TO ASK! WE DIDN'T EVEN ASK WHAT PRONOUNS THEY PREFER! WE'VE JUST BEEN SAYING 'THEY'!"

"'They' is fine," the human piped up. They then shyly looked downward.

"ah, so you do talk," Sans remarked. "so, wanna give us your name? it's fine if you don't. that question used to always bother me."

"...Frisk."

"hm. that's a nice name."

"IT IS A NICE NAME, BUT I THINK I'LL JUST CONTINUE TO CALL YOU 'HUMAN'." Sans snorted.

"heh. seriously, paps?"

"WHAT? I THINK IT HAS A NICE RING!"

XXXXXX

Accidently taking a wrong turn lead the group to Temmie Village. Although it wasn't dangerous, it was certainly weird.

"i don't think I wanna be around so many temmies again," Sans groaned.

"THEY WEREN'T THAT BAD," Papyrus protested. Frisk nodded in agreement, adding their own two cents.

"Cute." Sans huffed again.

"only as cute as they were confusing." The trio continued to walk.

"Um…" The skeletons turned to the human.

"what is it, kiddo?"

"Why...why are…why are you helping me?" Sans stopped. Papyrus did as well.

"YOU WANT TO EXPLAIN, SANS?"

"...not yet. i can't tell them when we're being watched."

"WHAT? THERE'S NOBODY AROUND HERE!"

"true, but they're still watching. they've been watching the entire time, actually."

"WHAT?! HOW? AND WHY DIDN'T YOU SAY ANYTHING? HOW DO YOU KNOW?"

"i just do. now c'mon. we're almost there."

"Where?"

"you'll see, frisk. you'll see."

XXXXXX

Sans was first to walk through the doors of the Hotland Laboratory. Inside was a certain yellow dinosaur.

"Oh! Y-you guys are here!"

"ALPHYS, YOU KNEW WE WERE COMING?" Papyrus asked, confused.

"told you someone was watching," Sans replied, natural grin widening. "see this monitor? al is able to keep watch over all of the underground."

"BUT HOW DID YOU KNOW WE WERE COMING TO YOUR LAB?"

"I - I had a feeling." Alphys turned to Sans. "S-so, um…"

"ah, yes. alphys, this is frisk. frisk, this is dr. alphys." The two bashful ones waved at each other. "so, al. you told me that you had remembered some things, right? about me? and you know, a certain person."

The bespectacled monster nodded.

"Y-yes, I - I remember quite a bit."

"even…?" Sans pointed at his face.

"Erm, y-yes I r-remember that."

"ah, so you do know a lot. huh. guess i could've answered the kid's question back in waterfall. but, y'know. can never be too careful."

"ARE WE GOING SOMEWHERE WITH THIS?" Papyrus asked impatiently.

"yes, yes we are. You first, alphys. after all, this lab is yours, right?"

"Y-yes. Well, i-it is now. You know it didn't use to be." Frisk looked at the two monsters curiously. They turned to face the child and the tall skeleton.

"frisk." Sans started. Alphys pressed the button to open the elevator door, and they all squeezed in. Once they reached the lower floor, both science enthusiasts spoke.

"Welcome to the True Lab."

XXXXXX

"S-so, Sans? You w-wanna explain everything to Frisk? " Alphys looked expectantly at him. Papyrus did the same.

"YES, SANS. IT IS TIME TO REVEAL THE TRUTH."

"yeah, i guess it is." Sans brought a hand to his face, only to set it back down. "um, kid. i know you'll be pretty surprised, so just. um. brace yourself for the shock, i guess." Sans put his hands to his face, only to remove them again. "uh. you prepared? 'cause -"

"Sans."

"yeah, i know, alphys. i just - i'm just a bit nervous -"

"IT IS ALRIGHT, SANS."

"but i never take it off! well, when i need to clean it, i do. but, like, i wear it in my sleep, pap! i -"

"IT IS ALRIGHT. YOU KNOW ALPHYS AND I DON'T JUDGE YOU. AND SURELY FRISK WON'T!"

"...yeah. yeah, you're right, bro. i'm being ridiculous. heh. here goes."

Sans lifted his hands.

XXXXXX

And with several whirs and clicks, the mask came off. His bony limbs went along with it, the illusion falling to show a light skin tone. A mop of white, choppy hair appeared atop Sans' head. When he opened his eyes, the others were met with a brilliant blue.

"heya."

XXXXXX

Frisk couldn't believe their eyes.

"Y-...you're…"

"heh. yeah. i'm."

Everyone stood with bated breath. Suddenly, Frisk dashed forward and grabbed San's mask.

"Wh-what is - what is this?! How does it work?!"

"it's a mask that creates the illusion of a monster, even to the person wearing it."

"...Wow…"

"i know, right? an old friend helped me make it." The child turned to Papyrus.

"Are...are you…?" He shook his head.

"I AM ONE HUNDRED PERCENT A MONSTER!"

"Y-you're probably surprised to see that Papyrus and Sans aren't -"

"stop." Alphys squeaked. "don't. you dare. finish that sentence. papyrus means everything to me, and he was one of the only people who who accepted and protected me when I got here. he's family, and that's something i've never had above ground ." At that, Papyrus gave a loud "nyeh" of agreement. "so don't you dare say those words." The royal scientist nodded apologetically. Sans turned back to Frisk. "sorry about that, kid. anyway, we brought you down here so we could create a mask for you as well. what do ya think?"

Frisk took a moment to collect their thoughts.

"...You've been pretending all this time."

"yeah, well. i had to hide. it was the easiest and safest option. i mean, what else are we supposed to do, walk around the underground and hope our souls don't get snatched?" Frisk glanced down before looking up again.

"...Do I have to be a skeleton? I mean, they're cool and all, but…"

"nah, you can be something else. so. are we doing this?"

XXXXXX

Sans knocked on the door to the ruins.

"knock knock."

"Who's there?" Toriel answered.

"kids."

"Kids who?"

"kid's dying to see you." At that, Frisk spoke up.

"Guess who?" The goat mother gasped.

"M-my child? Is that you, Frisk?" They giggled. "It is you!" The two could hear Toriel start to cry happily. "Y-you took care of them!"

"yup. you don't gotta worry about the kid, alright? 'cause papyrus and i are gonna keep taking care of them."

"Thank you. Thank you."

"it's 'snow' problem."

"Mom?" Frisk queried. "Would...it be okay if...we come in?"

"I...Yes. I will make an exception just this once." Toriel stood.

"oh. just warnin' ya. the kid'll look different, but it's an illusion." The door opened. Tori gasped again.

"Frisk?"

"Illusion." Sans reminded.

"O-oh, right. How…?"

"you wanna show her how it's done, frisk?" The child nodded and took off their mask. The dark facade faded. The goat stared in astonishment.

"That - that is amazing." She exclaimed, wrapping her arms around the kid. They laughed again.

"i know, right?" Frisk looked up at Sans. "huh? oh, you want me to…? well, alright. but only because she's seen me before."

"I...don't believe that I have?" Tori bleated, confused.

"oh, no. you certainly have," Sans chuckled, removing his mask as well. "see?"

Toriel's mouth dropped again.

"...S-Sans...You...Oh, my goodness, I thought - I - you're alive!" She rushed towards the short man, hugging him tightly. "Both of you, my children…Both of of you are...Oh, Sans, I've been talking to you this whole time! I didn't even realize!"

"heh heh. yep." Sans found that he couldn't stop a few tears from falling. "i appeared to be your punny skeleton friend this whole time. But truthfully, i'm sans the skeleton. i mean human. i got used to saying skeleton." Toriel laughed.

"Would you two like some pie?" Frisk nodded. Sans' smile grew.

"sure, tori. after all, it can only help to maintain this as-pie-ring moment." The trio laughed.

"Well then, come on. I already have one waiting."

"coming right up, mom. er, I meant momma. as in 'momma toriel'. Cause you're frisk's mom. eh heh. heh. eeeeh." The goat woman laughed again.

Hearing Sans call Toriel 'mom'...

It fills Frisk with DETERMINATION.