I Am Boring, but My Classmates Do Not Know What I Am Doing in Your Room.

Yuki Toyama, an introverted loner, has a secret he hasn't told anyone, that he and his classmate Yuzumi Takai are "sex friends." It was supposed to be a purely physical relationship. But when Marika Uehara, a popular girl in the class, begins to show interest in Toyama, their attitudes begin to waver.

*Note: Includes 3 extra chapters*