White Cage

Heita was secretly in love with his classmate, Komai, and was found out by the infirmary sensei, Tsuge. Tsuge threatened Heita, “If you want me to keep it a secret, you'd have to listen to me.” From then on, Heita lets Tsuge had his way with him. Soon, Heita found that his rationality could no longer restrain his own overwhelming urge and desire. Did he fall in love with Tsuge?
(from Attractive Fascinante)