Mesu Kyoushi: Injoku no Kyoushitsu

Takuya's parents divorced when he was young, and his mother remarried a man named Sanada. Sanada's son, Eiji, was a genius who constantly looked down on Takuya. Unable to bear it, Takuya left home and enrolled in a high school under his mother's family name.

One day, a new teacher arrives at his school: Eiji, his older stepbrother. Accidentally, Takuya witnesses Eiji meeting secretly with Miyuki, a popular female teacher, in an empty classroom. Determined to get revenge on Eiji, Takuya plots to seduce Miyuki with the help of Rihoko, the school doctor.