What could be strange about an ordinary student named Sorata Muon? Well, he has a secret life that no one knows about, and in this life, he is a skilled thief known as the Mouse, and there is no object he cannot steal. He is assisted by three beautiful girls who are deeply in love with him: Momoza Mei, a physicist and computer genius; Karibayashi Yoi, a chemistry expert; and Kazuki, a skilled fighter.