Undead Ninja is an arcade tactical role-playing game with an isometric view. During the Warring States Period, wars broke out everywhere in Japan, and people had little means of subsistence. The demons took the opportunity to wreak havoc on the world. On the sixth day, the demon king entered the world with an army of monsters, infecting Oda Nobunaga in his heart demon form, causing his temperament to become bloodthirsty and cruel: burning Hieyama, attacking Honganji, killing monks, and killing prisoners. The war continues and the heart demon's infestation spreads.