Saint Tail Vol 1

About Saint Tail

Meimi Haneoka is a 14-year-old student at St. Paulia Academy in Seika City who, during the night, secretly transforms into Saint Tail, a magical thief who steals from thieves to give items to their original owners. She gets help and guidance from her friend Seira, a nun-in-training, and she is chased by her classmate, Asuka Jr., who is obsessed with finding out Saint Tail's true identity.

Source: Anime News Network Encyclopedia