18+ Double Play

Tamao Hiroi, a second year high school student, is a former member of the baseball team. When he came home one day, someone was in his room. There, the most beautiful girl in his school and the ace of the softball team, Ran Homura, was masturbating while calling his name. He is soon found out though and a strange "master/slave" relationship begins.

(Source: Nihon Bungeisha, translated)