Hina, Natsuo's new step-sister and crush, is having an affair?! Natsuo and Rui join hands, and together, they frantically try to track down her scandalous lover. At last, they come face to face with the man in question, Shuu Hagiwara! However, Shuu declares that he has no intention of breaking things off with Hina. Just what sort of conclusion awaits this twisted relationship?!.