Man & Woman Sexology: Private Lessons(1974)

One day, Hara Nobuo witnessed his father assaulting Tokiko, whom he loved as a surrogate mother. Tokiko then committed suicide. As Nobuo grew up, he was still burdened with this horrible trauma and became sexually impotent. His friend Junichi tried to cure Nobuo's impotence. Then one day, Nobuo rescued Sachiko from being about to being attacked in a park. Since then, the two were rapidly drawn to each other...