Detective Kenmochi asks Hajime for help catching a phantom art thief, a so-called Kaitou Gentleman who leaves calling cards announcing his next target. He takes Hajime and Miyuki to the mansion of the master artist Gamou Gouzou. There, Hajime meets Sakura Izumi, a former school friend who has been declared Gouzou's heir based on a stolen painting of his daughter which was sent to an art competition by the Kaitou Gentleman...