Female College Student Volunteers as a Slave (1991)

Itsuko, a university student, has lost interest in her boyfriend Kume's weak sexual relationship and is having an affair with her university assistant. Meanwhile, Itsuko's classmate Yoko is giving sex lessons to Makoto, a high school student she tutors. Makoto's brother, Jin, is a playboy who preys on the female university students who are Makoto's tutors one after another...