Saimin Gakuen

Shinta Murakoshi is an extraordinary student at an ordinary high school. Every student hates him, even the teachers and parents hate him, and his life is in despair. One day, he receives a gift from his internet friend Mr. K.—a hypnotism gun, with which he can control the mind of anyone. He then sets out to turn all of his former (female) tormentors into his sex slaves. (Source: ANN)