Fourteen-year-old Meimi Haneoka is an ordinary girl by day, but at night she takes on the "position" of Saint Tail, a modern-day Robin Hood who steals from thieves and returns items to their rightful owners. She is assisted by her friend Seira Mimori, a nun-in-training, and pursued by her classmate (and future love interest) Daiki Asuka, often referred to as "Asuka Jr."