One day, Mai visits her uncle's house. Mai, who is in the midst of puberty, is curious about men's bodies and penises, and masturbates every day, unable to concentrate on her studies. "I'm a naughty girl. I need to be punished..." A childhood memory comes back to her. Her uncle used to scold her. He is the only one who can punish me... and so begins her masochistic training. Her immature ass is beaten red, and her budding breasts are tied up, as Mai awakens to the pleasure of being a masochist.