Kentarou inherited from his father "Bus-to Shinken", an ancient martial arts tenchnique that allows to change opponent's bust size by striking at certain body points. However, his flat-chested step-sister Rao has sworn to eliminate all boobs in the world using this technique. Obviously, Kentarou can't permit such travesty to materialize, so the fateful showdown is about to ensue!

A Hokuto no Ken/Fist of the North Star parody eroge.