Mesu Kyoushi: Injoku no Kyoushitsu

Based on the erotic game by Bishop.

Takuya's parents divorced when he was a child. His mother took him and she got married to another man, Sanada, soon. Sanada's son, Eiji, was a genius and looked down on Takuya. Takuya couldn't stand it anymore and left his house. He entered a high school ....