The heroine's reaction when the demon king appeared is so suspicious. Everyone was scared, terrified or something but she's blushing??? What kind of reaction is that, I mean, he's good looking yeah, but the normal reaction if someone is to appear so suddenly in thin air is to be scared, and that...
This one seems similar to the yandere otome game novel (forgot the whole title since it's long lol) where the all capture targets are yandere too
EDIT: It Seems Like I Got Reincarnated Into The World of a Yandere Otome Game, is the title of the novel that I'm talking about, if anyone's curious