Youjuu Kyoushitsu

Its hentai, and dark violent hentai at that.
The opening scene pretty much sets the tone, demon rapes school girl, she is "wrong" or somehow not powerfull enough of a host for his "seed" and her womb explodes upon climax and paints the walls of the bedroom this rape takes place in, personally, not my thing, but if you like gore, tentacle rape, and hideous monsters violating tender young women, then this is your show.