I think the story will be
of how chara became who they are. I imagine it'll play at the meta angle by saying that chara became apathetic to everything due to the player choices. As in, they realized there was no point in doing anything when you can be forced to do something at any moment. Meaning that they didnt see a reason to form bonds with anyone anymore. This plays into the intro of the game with the line which roughly goes "you cant choose to be anything in this world".