High school student Ookoshi discovers the secret of his well-endowed classmate, Takita—it turns out that Takita does not have the breasts that everyone around her believes her to have. Fearing that Ookoshi may expose her secret, Takita "gives" him something irresistible as an incentive.

After arranging a meetup with a girl online and thinking that it may escalate into something lustful, Ami's older brother decides to practice having sex with Ami. Of course, she is not willing to let her brother have his way with her, unless he completes a certain "challenge."