Ayako Inoue is worried about her son who has no interest in the opposite sex. She cares so much about her son that she decides to teach him about sex herself. Ayako's sexual education starts with teaching him how to masturbate, but it gradually escalates and eventually develops into her son's first time. Ayako, who is sexless with her husband and craves carnal desires, cannot forget her son's cock, and before she knows it, the two of them fall into a forbidden relationship...