Warning! There is a chance that there will be spoilers for the pacifist run of undertale. I recommend finishing that before reading this. There won't be any spoilers for the no mercy run, so don't worry about that! Also, don't worry about anything NSFW/lemon if that's not what you're into-there won't be any of that here. You're a human that's fallen down into the underground. You've decided that you'll stay instead of going home after fighting Asgore and sparing him. Now, you had made some great friendships while in the underground-but one of those friends in particular was one you'd like to be a little more than friends with... Aaaa an X reader fic! I haven't done one of these before, but I hope you still like it!

Paperjam wakes up, hoping it was all a dream. Only to find out... It was a nightmare.

Sans has lived through countless timelines. He's seen the kid make friends with everyone, only to give up in the final moments. He's seen the kid killed, over and over and over again. Sometimes, he'd even done the killing himself. And no one ever remembers. Not even the kid herself. It's an exhausting cycle, one that never seems to end. But there's something different about this run. Another human's fallen down... the kid's sister.