The Demon King's reign, known as the "Demonic Invasion," lasted for centuries, and countless heroes were defeated by the Demon King without any means to overcome him! However, the Demon King was finally slain by the hero Therios, known as the Last Hope. The world achieved peace, and the hero Therios disappeared somewhere--. But the Demon King, who was said to be dead, is revived by a miracle! As a dog...!? This is the story of the last Demon King, now fluffy, protecting his granddaughter, who is targeted by the entire world, and earnestly wishing to live in peace--.