Issei Hyoudou and the Occult Research Club return in standalone OVA episodes bundled with the High School DxD light novels. In one episode, a mysterious affliction shrinks the bust size of girls across Kuoh Academy, and Issei teams with Rias Gremory to investigate. In another, an ancient Egyptian sorcerer named Unas possesses Issei and proves every bit as lecherous as his host. These bonus episodes sit alongside the first TV season as supplementary side stories.