Metro

Mizuki Shiroiwa, who has been sexually repressed by his mother, is molested by a stranger on the train while going to school. Mizuki let it happen even though he could have gotten away. One day, Mizuki finds the man, Kurose Shinobu, and offers a deal. "...I want you to violate me more." Shinobu responds to the "command" of a masochistic Mizuki. However, in the days of indulging in immorality and drowning in desire, the emotionless Shinobu gradually began to change. A fresh and beautiful immoral boys love between a man with a dark past and a boy who suffers from sexual repression.

(Source: Home-sha, translated)