Teacher hentai shows obviously, teachers sexual relationship with their students. The Japanese word for teacher is sensei (先生) and it is commonly used as the translation to describe them in anime and manga.
Example Story: Cute girl have really bad grades. She really have to do better or else will have to repeat year again. But she hates studying. So she approach her homeroom teacher and asks for better grades, with her naked body on stake.
Related Tags: Tutor Hentai, Coach Hentai, Female Teacher, Male Teacher