Ishidou Natsuo is a gifted girl who can achieve anything she wants in sports. Because of this she is permanently bored, as there aren't any real challenges to her abilites to make her feel alive. One day she receives an invitation of a merry girl to join her martial arts club. Irritated by her happy expression, Natsuo decides to accept the invitation just as a pretext to beat her up, but she receives a shocking surprise.