A father-son household. The father, seeking private tutoring for his son who is preparing for exams, hires Yuri-sensei, a married woman who runs a private cram school in the same neighborhood and is known for her talent and beauty. She has been helping the son since he was in ● grade, and he calls her 'Yuri-sensei.' One day, the son asks Yuri-sensei to show him her butt as a reward for improving his scores. Unable to refuse, Yuri-sensei reluctantly agrees, saying 'It's our little secret,' and shows him a bit of her plump buttocks. From there, a chain of forbidden events begins...
