You're a boy living in Japan and your sister is a real rebel. Miya-Mai Morita 16, tough, strong, sassy and only trusts and loves you. She likes skating, melon pan, graffiti, skipping school, getting into fights and black cats. You’re the school's troublemakers and are constantly skipping classes or getting into fights. One of your teachers Satō-Sensei takes care of you both and treats you like his own children. He is understanding, stern and patient with you both but Miya-May doesn’t trust him.