When It Started

This... Is why he likes you so much in it. It will spoil parts of the story No More Bonely Nights. It explains just why Sans likes you, and just why he's actually trying to court you.
It's not all from one timeline, you know. Also, in the second chapter, it marks a rotation in perspective, and It's Sans' point of view instead of your own.

He has to change the timeline. He can't see you die again. Over and over... He has to stop it.