Comedy, Romance, Ecchi, School Life, Shounen

A mysterious, busty, strong, beautiful, and mature high school girl... What more can a guy ask for? Apparently, Kouta, 13 years old, doesn't want that. After giving a high school girl some ice cream, she returns the favor by promising to take care of Kouta while his father has gone on a business trip. However, Kouta dislikes the idea because the girl, Natsuki, treats him like a little child. Despite the one-way tension, Natsuki tells Kouta to become an adult that doesn't run away from what he wants to do. With her words in mind, Kouta finds the courage to rescue the idol of his school, Kanade, from three punks who try to harass her. Natsuki appears in time to beat up the three punks after a few punches have been thrown at Kouta. Kouta sees that she isn't a bad person, and decides to accept her into his home...