A year ago, Emiko (RYU) separated from her husband and has been living with her son Ryosuke. One night, Ryosuke accidentally sees his mother masturbating in her room, developing strange feelings towards her. Unable to hide his excitement after seeing his mother's usually unseen sexy side, Ryosuke confesses this to her and tries to push for a relationship. Though confused, she agrees under the pretense of "sex education" and begins guiding him about sex using her own body.
