The son Shinya's friends, who often come to stay over, are secretly attracted to his mother Yumi. One day, Takanori accidentally witnesses Yumi masturbating and involuntarily attacks her and has sex with her. Another night, he approaches Yumi again, but Michio joins in and enjoys her voluptuous body. When the son goes away to a training camp, he gradually begins to seek out the young people who engage in a threesome orgy, and he climaxes violently.