A 14-year-old girl becomes a phantom thief by night, stealing from thieves to return what was lost, and her classmate is the only one who can catch her. The romance isn't a subplot waiting to happen, it's built into the fundamental tension of the show, two people on opposite sides of the law who keep almost recognizing each other. This is a magical girl show that treats the heist itself as the magic, not a transformation sequence.

Meimi Haneoka lives a double life. At fourteen she is an ordinary girl during the day, but at night she becomes Saint Tail, a present-day Robin Hood who takes stolen goods back from thieves and hands them to the people they belong to. Her friend Seira Mimori, a nun-in-training, helps her, while her classmate Daiki Asuka, known as Asuka Jr., tries to catch the thief and soon becomes her love interest. Genre-wise, the show is a magical girl adventure with fantasy and romance running through its nighttime escapades.