Sex in anime, manga and anime PC dating sims games. Has a possible chance of tentacle rape and any other pervy elements.
It's hard to keep it away from little kids or anyone else under 18 away from it due to:
Them being total anime fans and looking into it more for characters designs, action and other stuff
because someone used it on characters from their favorite shows like Sailor Moon, Pokemon, and Naruto.
Hentai is also a very controversial genre in the anime world.