Gedou Gakuen Iinkai

Ten years ago there was a rumor of prostitution organization inside the school that never spared its members who leaked its secrets. At present time such rumors have revived with mysterious suicide of one of the girls.
Main character who is school president is set to uncover the secrets of the organization. In this war he needs to use his own libido to break mind control of the girls.

[From vndbreview]