Mariko is a PTA officer at her eldest son's junior high school. One day, the chairman of the PTA suggested that they hold a party to celebrate the school festival, including the teacher. They had a great time at the first party at an izakaya, and went to karaoke for the second party. Meanwhile, the sexually frustrated Mariko has her eye on her eldest son's teacher. She uses her experience and maternal instincts to seduce him. Eventually the two of them get into an affair.