A good portion of the chapters is spent with the girls going crazy over the MC. Especially the "love interest" which for a very long time, until the last 10 chapters or so played the overly attached, stalker, jealous girlfriend (apparently some people around here consider that love, whatever).
... was the solution to the problems. Basically, he gets handed a diary that his future self provided, to use that to save the world. How does that even make sense?
Turning a demon into a boiler using brainwashing... that's messed up on so many levels.
when he took the body of an innocent dead girl to try to revive her, but found another use for it later.