Kousaka Kyousuke, a typical 17‑year‑old high‑school student living in Chiba, has struggled to connect with his younger sister Kirino for years. Kirino, who is now fourteen, has long ignored Kyousuke’s presence and looked at him with disdain. Their relationship seemed doomed to stay fractured. One day, Kyousuke finds a DVD case for a magical‑girl anime that has fallen into his doorway.