انیمه Wanna. SpartanSex Spermax!!!

Based on the erotic game by Guilty eX.

Tanabe Yoshiyuki disappears because of the frequent oppression done to her at school. Nagisa, Yoshiyuki's cousin, decides to dress as a man in order to find out what happened to her and take revenge on those responsible for the persecution.

(Source: Translated and Edited from Nekopoi)