Kusakabe Maron, an ordinary high school girl outwardly, is the modern embodiment of Joan of Arc. Guided by the angel Fin Fish, she assumes the alter ego of the phantom thief Jeanne by night, purifying artworks possessed by malevolent entities feeding on the emotions of their owners. Branded as a criminal for the disappearance of these artworks post-exorcism, Maron faces a dual life. Her routine is disrupted by the arrival of a new neighbor and classmate, along with the emergence of a rival thief named Sinbad. Complicating matters further, her closest friend happens to be the daughter of a determined detective bent on apprehending her. Balancing these conflicting dynamics, Maron navigates a challenging path in her mission against darkness.