Sensei no Okiniiri!

Misuzu just started her dream job teaching at a prestigeous high school, and she feels totally motivated. Recently, she began going out with the really hot/manly principal Kazuki, and their relationship couldn't be better. But one day, Misuzu had sex with Kazuki's younger brother Masahiro, who happens to be one of her students. This is a huge secret that they can't tell anyone: the love affair between a teacher and a student.