Rope and Boys 3: Otokoro Hell 1993

Directed by Takaaki Hashiguchi

A gay college student who has been in love with his childhood friend for over 10 years. That male friend and his girlfriend find out that he's gay and tell the whole school about it. In order to take revenge, the hurt protagonist asks a gay acquaintance to imprison his friend and train him in SM, trying to make him learn the taste of men...