Body Jack: Tanoshii Yutai Ridatsu (1987)

Dr. Toyama takes control of the body of a beautiful girl with his strange invention. He lets the young Asagedani "slip into" her body so he can see how it real feels to be a girl. Then Komaba's classmate, the equally beautiful Nakano, surprises "him" and mistakes his activities for a sexual advance from her friend.