Yakin Byoutou Zero

This is the back story of how the genius doctor Hirasaka Ryuuji acquired his perverted pastime as a med school student. He and Jinguuji Narumi are rivals at the top of their class. One day, Narumi tells him that if he can seduce the woman she designates in the 2 weeks before graduation, she'll admit her defeat and do anything he tells her. The girls she suggests are just as beautiful and desirable as herself. Sensing his perverted perceptions transforming into a talent at her tantalizing suggestion, he readily agrees.