According to whispers, if a young girl makes a pact with a white fairy, it will fulfill any wish she desires. In return, she becomes a magical girl and must risk her life to defeat terrifying and vicious witches.
Iroha Tamaki, a gentle middle schooler from Takarazaki City, proves these tales are real. Armed with a magical crossbow and the power to heal wounds, Iroha searches for the labyrinths where witches lurk and eliminates them before they can attack humans. However, Iroha cannot recall her wish, and even Kyuubey, the white fairy himself, seems unaware of what she asked for.
One day, Iroha hears about a city where "magical girls can be saved," and finds herself boarding a train to Kamihama City at sunset. Unfortunately, she learns that the witches there are significantly stronger than usual. After veteran magical girl Yachiyo Nanami is forced to rescue her, Iroha swears never to return. But when a chance meeting with a tiny Kyuubey seems to stir faint memories, Iroha feels compelled to explore the mysterious city despite the peril.