Hey y'all, I'm looking for the name of a hentai manga that I read at some point.
A high-school girl is going to confess to the guy she likes, but finds out that he's having sex with his step sister. The reason for this is he has some kind of condition where he becomes a total beast if he doesn't have sex once ever hour or so. The step sister then "trains" the new girl to become his wife and fulfill his needs.
Picture more or less unrelated.