Need help finding
I read a while ago a doujin but can no longer find it. The premise goes about this nerd that meets with this girl. The guys is unassuming but the girl is very flirtatious and they both end up doing it. Unbeknownst the girl is actually a Succubus/demon and had placed like a demon seed inside him. It starts to corrupt him, and he assaults one of the school girl in the library. When they finish, he fills instant regret, but the girl starts to change and becomes a succubus as well. The first girl tells him that everyone he fckes will become a succubus as well, and she temps him more and more. Eventually he gives in to his urges and transforms everyone into succubus, before he himselfs transfoms into the Demon King
I'm 80% certain I found it in this subreddit but I honestly can't remember, if anyone knows please do let me know