Reiko is 46 years old. Lately, she's noticed her son giving her intense, heated glances. It's almost her period, so she's inserting a tampon when her son walks in. This sparks a sex education lesson, as she tells him, "Women have something called menstruation." Gradually, Reiko becomes curious about her son's crotch and makes him pull out his cock. She carefully explains male physiological responses. Soon, she extends this "education" to her son's friends when they come over. The story unfolds as a lustful mother indulges herself, devouring one young cock after another.