Meimi Haneoka is a seemly ordinary student at St. Paulia's Catholic school by day, but at night, she becomes the mysterious and magical thief Saint Tail! With the guidance of her best friend (and nun-in-training), Seira Mimori, Saint Tail is steals back the treasures that were stolen from the innocent.
But despite her virtuous motives she's still a thief and her classmate, Asuka Jr., the son of a famous detective, is determined to discover Saint Tail's true identity. Of course it doesn't help her case that Saint Tail has a secret crush on her pursuer and leaves clues for the young detective. Will the young sleuth catch her this time? Or this time, will she steal his heart?