Demonbane is a Japanese visual novel and anime series that blends elements of mecha and the Cthulhu Mythos. It follows the story of Kurou Daijuuji, a private detective who becomes entangled in a battle against dark forces when he discovers a powerful grimoire. He partners with a mysterious girl named Al Azif to pilot the giant robot Demonbane. The series is known for its unique fusion of genres and its intricate plot, offering a thrilling experience for fans of both mecha and supernatural themes.