The main story

Once upon a time,

there were two races humans and monsters. One day war broke out between the two races. Humanity was victorious and sealed the monsters underground with a powerful spell. One day a child fell into the underground. But, with their determination, They now control the monster's fate. And their choice? To murder everyone over and over again.

The human killed all the monsters many times with the power called reset, the human thought that there would be no consequences of their actions. But then he met Sans, a lazy skeleton with no sign of power whatsoever. A skeleton that made the human feel the sins crawling on their back, a skeleton who killed them so many times that they were close to giving up. But they didn't, they were determined, and once they finally killed Sans, it was time to start over.

This went on for weeks, months, years. There was no escape from the power of the RESET. In every reset, everyone except the human lost their memories, and it all started over. The human gathered skill now it was a walk in the park to kill everyone in the underground. Until that one timeline, where when sans was supposed to die, he dodged this was a major glitch and caused the files of the game to become corrupted, resulting in Sans remembering how many times he and everyone he cared about died. Sans, distracted by this, took a hit and dusted away once again.

This time sans remembered after the reset and he was not happy, he first told what happened to papyrus, he didn't believe him and said it was only a dream. later on, sans went to talk with Undyne, Undyne didn't believe him and said that there was no human with such power, with overconfidence. then he went to talk with dr. alphys, alphys was confused. how sans, a lazy skeleton who hardly ever stays awake, could come up with such an absurd theory. alphys asked sans that what the human looked like. sans explained frisks look and, alphys was shocked, she said that a human that looked the same had entered snowdin about 15 minutes ago. sans quickly got up and said that he would face the human and that alphys should start evacuating the monsters of the underground.

sans arrived at snowdin and panicked and found papyrus fighting the human, papyrus said that he looked panicked but while papyrus was looking away, the human quickly slashed him down, killing him. seeing this weird effect the human immediately reset and did the same thing, genocide.