Maron is 16 and a seemingly ordinary high school student. She is extremely gifted in gymnastics. Her alter-ego is Kaitou Jeanne (phantom thief Jeanne), the reincarnation of Jeanne D'Arc. Through the angel Finn, who is sent to help her, she receives a mission from God to seal away demons who have come to Earth to steal the beauty in human hearts. The demons, which are hidden inside objects of great beauty (usually pieces of artwork) are captured when Jeanne hits them with a pushpin and shouts "Checkmate!", turning them into chess pieces. She is a lonely character who hides her feelings behind a warm smile.