Okay so I just wanted to put warnings right up here where you can see them immediately, a large portion of this chapter is a depiction of an abusive relationship. I don't want to cause anyone harm so if that will bother you, skip down and read the end notes and I'm going to put a summary of the events that hopefully won't cause any problems. And if it gives you an idea about this chapter, I was listening to Paralyzed by NF on repeat through a lot of it. It reminds me of Sans more than Red at this point in the story but hey when have I ever made sense.
Anyways
Here's wonderwall  

Sans woke up with his face pressed into a pile of papers. He sat up slowly, groaning as he stretched. He rubbed the back of his neck as he stood all the way up. Last night, after Papyrus had forced him to eat a large amount of his awful spaghetti (Sans had never fully appreciated how much his brother's cooking had improved in 17 years until that moment), he had come down to the basement, poring over Gaster's notes for any clues as to what had happened to the machine.

It didn't much help his research that every single mention of multiverse theory was gone. Entire papers, even footnotes to the vanished papers that he knew had been there before, had just disappeared without a trace. There was nothing left, and Sans was beginning to get to the end of his rope. At least he had gotten some sleep.

He wondered if Red had been able to sleep for a moment before he shook his head and began to pace.

Even if he continued to go through the papers, he doubted he would find anything useful. What else could he do? He knew that he was going to have a very, very long talk with the kid when they got there, but they weren't due for another couple of hours at least. There was no one else to talk to, no one else who even remembered the resets or knew about the multiverse. No one could even begin to understand--Sans lifted his head slowly. Well. There was one person, wasn't there? Not that 'person' was really the right word to describe that little asshole.

X-X-X-X

Boss threw him down onto his back, hard. He drew back his boot, preparing to kick his already broken ribs. Red tried to scramble away, only to get caught up by the pain in his everywhere and he couldn't get away, he couldn't escape, Boss was going to hurt him again and he couldn't do anything to stop it and oh God he couldn't take any more and suddenly he could see Boss's face and he found himself screaming, screaming for mercy, screaming for someone, anyone, to help him, to save him from Boss, his screams becoming more and more incoherent until he was asking "Don't you love me?"

The expected pain didn't come and Red allowed himself to peek up at Boss through his fingers. He had set his foot back on the ground and was instead reaching for the hood of Red's jacket. Red started to sob quietly as he was wrenched up to eye level. "What did you just say?" asked Boss, far too calmly.

Red knew that he should shut up, he remembered how much worse it got the more pissed off Boss was. But his body betrayed him, his weak, hope-filled soul almost forcing him to forget all of the warning signals coming from the rest of him. His mouth opened and he started to babble, the words coming so quickly they were damn near incomprehensible. "D-don't you l-love me? We're brothers, I k-know we used to l-love each other, r-right? We used to- used to l-love each other s-so much, and you even s-said you n-never stopped, even now, you j-just didn't know h-how to d-deal with it, you b-barely knew what l-love felt like because of this stupid, f-fucked up world. You l-love me, you p-promised, you promised, youpromised, youpromisedyoupromised!" His sobs were getting louder and his whole body was shaking and he had no idea how to feel about any of this, this was his brother , this was the same person that had been holding him and crying just three days ago, he couldn't be gone .

Boss just stared at him for a moment, and Red felt something like hope blooming in his chest. Maybe Fell had remembered it wrong! Maybe this Papyrus had only needed to be told what he was feeling, maybe he really did feel something brotherly about this and he would put Red down and he would fucking stop, maybe-- Red was suddenly back on the floor, gasping in pain and fear and some small measure of possible happiness. He looked up.

Boss was smiling. But it wasn't the smile that Red had grown used to, the one that only Red and Sans's brother had ever really been able to coax out of him, one that expressed the happiness and peace that 17 years had given him. There was no joy in the smile that Red was seeing now, not even an echo of the one from his memories. There was nothing good in this smile at all.

"How could you possibly think I could ever love someone like you?" Red froze. No. Nononononono that was his brother's voice but he couldn't possibly be saying-- "How could anyone ever love you? Hell, the only reason no one has killed you yet is because of our...familial tie" Boss's expression was one of disgust, as though someone had presented him a particularly strange-looking bug, the thought of being related to Red at all apparently so repulsive that he had to pause for a moment. "You are nothing to me but a burden, you useless piece of shit"

Red's sobbing had stopped at he stared at his brother in shock. He had never heard his brother say this before. He supposed he must have known it, but even before the Undertale brothers, in any reset, Boss had never actually said it .

Again, his shock drove him to make the stupidest of mistakes.

"P-papyrus... please ..."

And with that, the smile fell from Boss's face and Red felt his soul turn blue right before he was thrown into the wall with a sickening crunch. Blackness began to fade in just in time for Red to let his eyes fall closed.

X-X-X-X

An hour later, Sans had managed to head off Papyrus by telling him that he was going to be late to work. Papyrus had seemed so thrilled when Sans had showed signs of caring about his job. Oh well. What he didn't know wouldn't hurt him.

Sans approached the doors to the ruins carefully, listening for any noise. The little weed wasn't particularly consistent, and it was still early, so he wasn't very surprised that he wasn't out of the ruins yet. He sat down with his back against the door. He thought about knocking, to see what Toriel was up to, but he realized he didn't really want to talk to a Toriel from 17 years ago. She had been...bitter. Sad. He had enough sadness right now, and she wouldn't miss his knocking, since he was usually at Grillby's at this point in a reset.

He leaned his head back. It was truly amazing how much had actually changed in 17 years.

He let his eyes drift closed.

Sans was awakened for the second time in the same day by a strange feeling on his face. This felt less like paper and more like...hair? No...it was too concentrated to be hair. But he could feel individual strands brushing against his cheekbone. He cracked his eyes open, only to be met with a face very close to his own.

He screeched and jumped back in a manner that wasn't particularly dignified, but succeeded in tossing the owner of the face away from him. Sans stood up quickly looking around. There was a bucket of paint on the ground, and a paintbrush laying on the ground next to it. He had the mind to realize that that was what had been touching his face, but as he glanced around quickly, he saw no one.

What the actual--

"Gee, thanks a lot for that!" came a tinny voice from somewhere by his feet. Sans looked down in surprise at the little yellow flower on the ground.

"Flowey!" He said, smiling in relief. That felt weird. He was pretty sure he'd never said that name with any measure of actual happiness before in his life.

Flowey looked confused by this new development for a moment, then he put on his big, fake smile. "Well howdy there, smiley trashbag!"

Sans huffed in impatience. "Cut the crap, Flowey. How much do you remember from the last reset?"

Flowey didn't lose the smile. "Well, not too much, I suppose! It seemed like a pretty normal pacifist run to me!" Then the smile did falter slightly. "How did the sun feel, Saannsyyyyyyy?" he said in a mocking voice.

Sans cursed under his breath. He'd forgotten what had happened to Flowey, but he supposed he should have remembered, considering how peaceful his life had been for 17 years. "What about this reset?"

Flowey gave him a strange look. "I think I remember this reset just fine, trashbag. I'm not decaying completely yet"

"No, no. I meant, is there anything weird this reset?"

Flowey giggled. "Well, I'll say! Frisk hasn't fallen!"

Sans froze. "What?"

Flowey grinned when he realized Sans's distress. "The little bitty human hasn't fallen into the underground!" he gave a loud, mocking gasp. "Oh, no! Does that mean they're not coming?"

Sans was still frozen. Something was seriously wrong. Frisk always came on the first day of a reset. That was the whole point of a reset, that they could start over. Unless...something else had caused the reset?

Sans realized flowey was curling his vines around his legs, almost casually. Sans had dealt with this often enough that he knew what was coming and that he definitely did not want it to happen. He kicked the vines off of his legs, one of which knocked over the can of paint that had been sitting on the ground. "Fuck off, petals" he growled.

Flowey just giggled again. "Aw! You're no fun at all! Well, see you later, trashbag! Maybe we'll never reset again and what I do will actually stick this time!" Then he was gone.

Sans sighed and ran his hands over his eye sockets. The little--

He frowned as he felt something wet on his cheek. Oh, right. Flowey had been painting on him when he woke up. It was probably very flattering and something that he should leave to dry forever. Sans snorted and turned to head back home. Time for plan B, whatever the hell that--oof!

Sans ran smack-dab into someone who was a little shorter than he was. He stumbled back, rubbing his sternum and looked at them. His heart leapt.

"Red!"