Sex education for her adorable son. A mother in her fifties opens the forbidden door. [Episode 1] Her son begins to masturbate while thinking about his mother. Seeing this, the mother helps him masturbate. [Episode 2] The mother is worried about her shy son. Ryoko feels uneasy as her son gives her sexual attention. [Episode 3] The mother sees her son masturbating. The son has lost control and starts to pressure his mother wherever he goes. [Episode 4] Feeling sorry for her son, the mother gives him sex lessons to get him used to women.