Ryoko, a mother, worries about her shy only son. One day, she finds a sticky stain on her son's underwear and discovers her mother's underwear in her son's room. Realizing that her son has sexual problems, Ryoko uses her own body to give him a sex education. However, her son is fascinated by his mother's beautiful, ripe body. He attacks his mother as she indulges in secret masturbation and forcibly thrusts his penis into her vagina, but Ryoko is happy to accept her son's growth.