Thanks for the update, and honestly avoid the supernatural/ fantasy side. You could include characters from those franchise but without the supernatural thing, in turn it will also makes him wonder it's all a normal world or a fantasy one, for later to realize that it was a waste of time lol
You can continue slice of life. My opinion is instead of the MC going to other worlds, make the girls come to his world. iIthink it's much better. It's just an idea