"Dear Lord, forgive me for the tricks up my sleeve..." In the world of phantom thieves, one ponytail stands out from the rest—the uncapturable Saint Tail! She is known not only for employing wild magic tricks during and after her heists, but also for reclaiming items that were wrongfully acquired. This notorious enemy of the law is the secret identity of Meimi Haneoka, a 14-year-old student at Saint Paulia's Private School. With the assistance of her friend, the nun-in-training Seira Mimori, Meimi adopts her alter ego at night to aid those in need. While her heists typically proceed without a hitch, things begin to change when a certain boy starts appearing during her ventures—enter Daiki Asuka, known as "Asuka Jr." because he shares his name with his father, a well-known local detective. He not only declares his resolve to be the one to capture Saint Tail, but is also Meimi's classmate at school! Following the young detective's first nocturnal encounter with the now-wary magician thief, a cat-and-mouse chase begins.