While staying at his older brother's house during his ronin year, Ryo becomes infatuated with his beautiful, big-breasted, and elegant sister-in-law, You. You, dissatisfied with her relationship with her husband, finds herself climaxing daily through masturbation. One day, Ryo accidentally witnesses You's affair with her lover. Unable to contain himself any longer, he confesses his desire to her at night. As You straddles him, revealing her voluptuous, swaying breasts in passionate surrender, Ryo discovers a new, intense emotion.