Emiko (RYU), who separated from her husband a year ago, lives with her son, Ryusuke. One night, Ryusuke sees her mother masturbating in her room, and he develops a strange feeling towards his mother. Ryusuke, who can't hide his excitement at seeing her mother's sexy appearance that she doesn't usually show, tells her mother about it and presses her for a relationship. Her mother is confused, but she agrees, "If it's sex education...", and begins teaching sex education to her son with her own body.
