"By that you mean..." the human starts, pointedly not looking at Sans as they think on their response, "You must mean Papyrus, right?"
Sans closes his eye sockets for a moment, exhaling visibly before his shoulders relax.
"yeah. i knew you'd figure it out on your own eventually, so i'll make this very clear–" he begins, but Frisk's disposition is making him cut himself off. They are smiling, but there's some timidness in the way they stand, their short body hunching over.
Sans rethinks his phrasing in a quiet second or so.
"heh. well, seems like you already get the jist of it. don' even think about goin' to bombard him with questions. if i find out you've been attempting it, well..."
The way Sans straightens up just a bit, tensing as he meets the human's eyes, they can already guess the response.
"...I'm gonna have a bad time?"
Bring it on, comedian.
Frisk softly shakes their head, nose scrunching up.
"not a good time, for sure," he confirms quickly after, winking ever so casually despite the mild threat. "if you have more of yer questions later, you bring 'em straight to me and only me. speakin' of which, i was gonna show you another thing as well."
"Are you going to tell me about Gah–" Frisk pauses when Sans gives them another one of his unsettling stares, "...about, that guy?"
"settle down. im gettin' to it. 'sides, you're really gonna try and deny me the fun of taking ya on tour? if i'm gonna explain, might as well do it in a way that pleases us both," he replies easily and leans back in his chair, then stands up and pockets his hands.
"Figures you would make me walk all that way for nothing..." Frisk mutters in passing.
"here, let's take a shortcut back to the house."
Now the human takes a wary step back.
"Not like before, right?"
Sans chuckles.
"i'll make it easier on ya this time," he promises, nudging his head toward the end of the platform. Frisk sighs and walks into that direction, the skeleton quickly catching up with them.
As they approach the connection between two platforms, there is a flash of black, but it's nothing like before. It's more like the way the human is used to being transported.
Following the short darkness only in front of them, they see the view of the skeleton brothers' living room opening up in front of their eyes. They walk forward with Sans at their heel, and when they're inside and turn around to face him, it's like they never even were in Hotland. It's just the house all around them.
Sans' smile is relaxed.
It doesn't last very long. He hesitates with his steps as he approaches the kitchen, and his gaze darts to the floor. He pauses, takes a breath and glances at the upper level of the house.
"paps?" he calls upstairs, then waits a beat. When there's no response, he shrugs and enters the kitchen. "alright, kiddo. before i explain to you about everything else, i'm going to show you exactly what your little time-bending powers do. sound like a plan?"
As he speaks, he reaches up to one of the cabinets and finds himself a pen and a couple sheets of clear paper.
"You will?" the human asks, pleasantly surprised as their brows shoot up.
"yup."
Sans takes his place by the table at the side of the living room, putting the sheets down and twirling the pen once in his left hand. Soon he gets it to settle right between his bony fingers.
He turns to give a side-glance to the human and nudges his head in an inviting gesture. They walk over to the table, then look down at what Sans is supposedly about to draw or write for them.
"okay, so..." he breathes, then goes ahead and draws a long, straight line across the paper, leaving a bit of space at the top and bottom, "this is the timeline. easy to see since it's literally a line, right? anyway," he makes a little mark near the top of the line, then taps at it with the tip of his pen, "this is where you drop down into the underground."
"Uh huh," Frisk nods their understanding, unsure where this is going. They wonder what's about to happen to that line as Sans keeps drawing, so they don't ask any questions that might interrupt the explanation.
Sans gives them a brief glance before he continues, making sure he's being as clear as possible. He doesn't want to have to explain it a second time.
"so yeah, normally you would just keep followin' this line, right?" he says, dragging the tip of his pen along the visualized timestream. "there would be no weird marks across the way, no 'checkpoints' you can return to. however, with the way things are now, the timeline looks more like this."
As he says that, he draws more dots at certain intervals all over the line.
"these are the points in time you can loop back to. now, i dunno where all of them are exactly, but ive figured a few out when you go back a lot in the same spot."
The human blinks twice.
"'Loop' back to? I don't get it. It's a Reset, not a loop?" they frown at the skeleton, who lowers his gaze and shakes his head.
"nah, kid. that's not how it works. after all... you did still experience all that stuff, and you recall experiencing it too, doncha?"
"Wha–W-well, but that's..."
They're at a loss, blinking rapidly now. Their throat threatens to close up.
"uh, don't take this literally, but the universe recalls all of that too," Sans then explains, his voice just a tad quieter as he goes to drag the tip of his pen over a part of the line once more, "when ya go back here, youre not erasing the time you spent there. you're just going back to this point in time, kind of like through a modified wormhole..."
He draws a loop that starts and ends at one of the Reset points, then faces the human again.
"i considered that these little points here might be wormholes affected by your determination somehow, but that theory has some problems. so i've moved onto other guesses, too," he says briefly, shrugging.
The human still seems frozen in their spot, trying to get their thoughts in order. The Resets... They're not actual, 'True' Resets? They know that Flowey always remembered before this, and sometimes the monsters would say things that made them think...
They blink again, many times, trying to get rid of the moisture in their eyes. No wonder then, they think, biting the inside of their cheek.
"kid, you alright there?" Sans asks, almost looking like he's furrowing his brows. Frisk sniffs as they meet his gaze, smiling wide.
"I'm fine," they try to say as cheerily as they can manage, and to their relief, Sans doesn't try to dispute that.
Since there's now a silent moment, the human decides to take a breath and ask something before the skeleton continues his explanation. If he's going to.
"So, uhm, Sans...? You were a scientist in the past, or are even now, I guess. That much is pretty friggin' obvious," they chuckle awkwardly, "But um, what kind of scientist exactly? I don't know too much about this stuff."
Sans shuffles, and for a moment they think he's not going to answer.
"astrophysicist," he eventually fills in, sounding almost wistful in just one word. The human raises a brow.
"Astrophysicist? Like the people who study space?"
That's as far as their knowledge on the topic goes, so it's obvious they'd be confused. It would be kind of hard to study space when you live underground. Sans shrugs.
"uh huh. but that's not all there is to it. astrophysics focuses on space, but more than that to how certain things work in space. i already mentioned wormholes as an example. black holes are also something astrophysics is trying to explain..." he pauses here, "and, another area of it is also the study of time and the possibility of time travel."
Their eyes widen.
"Oh." Well, that suddenly explains a lot.
Sans sighs and rests the elbow of his free arm on the table, then leans his head to his palm. Standing straight has become too much effort.
"also a big part of why getting to the surface was important to me, y'know. before all this," he gestures to the timeline-drawing on the paper with his pen, "started to happen. might as well admit that now."
His voice turns into something more like a mutter by the end.
Frisk frowns, not exactly wanting to look at his face right now. Just another future they're taking away from one of their monster friends. Another wasted dream. The urge to suddenly Reset bubbles in their stomach–the urge to erase this moment. They try not to think about it.
Sans shifts slightly and another scratch of the pen is heard. Only then does the human return their gaze to the paper.
"y'know, since you keep loopin' back an' not actually 'resetting', like ya thought before, i'm sure i... the me that remembers you killin' everyone, found it important to try 'n stop you."
They frown as they chance a look at him. Sans is looking back at them, seeming serious despite still having the little beads of light visible in his eye sockets.
"You saw Chara, even if you didn't know who they were at that time, right? And you knew who would be in control of the loops from then on, if they got a complete hold on me," Frisk speaks softly, feeling a bit unsteady on their feet.
"that's what i think happened," Sans hums, "but also... that wouldn't've been my first time encountering someone with stats as high as that. And... It didn't end well then, either."
His voice goes so dark, Frisk has to look up at him again. And just like they thought, now those little white lights are gone.
They take a guess on who that person may be, but they're not certain. They don't want to ask when Sans is looking so scary. They swallow and hastily think of another thing to distract him with.
"Err, this might sound a little stupid. But. Are you sure I keep going in loops all the time? Because, well, when I do a really big loop after the barrier has been brok–" they pause when Sans' empty gaze meets them, and they flinch, but don't stop talking entirely.
"W-when the barrier has been broken and Chara kind of urges me to go back. After that, everyone has clearly forgotten completely. And... Well, some things might happen a little differently without my interference at all."
Sans closes his eyes, seeming to collect himself. He relaxes a moment later, his normal look returning.
"that doesn't mean yer not still loopin'. it just means there's some other things at play. 'sides, spacetime is really wonky nowadays," Sans says, his voice a little strained in the beginning since he's still coming down from that moment of tenseness just now.
"and i assume those changes aren't all that big, otherwise ya woulda said something sooner. so it's either some anomaly or shift in the dimensions, or jus' a normal butterfly effect. you can travel back in time, i wouldn't think you'd be so surprised by things not comin' out normal after you do it."
Frisk shows a sheepish expression.
"Yeah, I guess I shouldn't be."
They're just relieved they managed to bring him back to a more easy mood.
Sans takes a moment to twirl the pen in his fingers again, then stands up straight, no longer leaning to the table.
"so to recount. now ya kinda know how i move between space..." Upon the look the human gives him, he can only bring himself to smirk. "hey, i did say 'kinda.' anyway, ya know how that works. ya know how i follow your movements in the timelines, and ya know yer loopin'. the only thing for me to explain is how all'a this is even possible, so..."
When Sans is about to shift their surroundings once more, he startles by footsteps just above. The footsteps are followed by a loud but hesitant voice.
"SANS?"
don't tell me he heard.
"SANS, PLEASE DON'T."
he heard.
[A/N] Hope you enjoyed my nerd-out.