After the life-and-death battle in Ente Isla, Mao and his friends return to Japan to continue their daily lives. From the Demon King asking his minions to give him a haircut, to the hero relieving tension at the gym. However, as comfortable peace returns, there are still mysteries that remain unknown to Chiko. How, indeed, did the powerless demon known as Satan manage to become the Demon King in the first place;