Ignir Lamprok, powerful mage of the Estria Empire, accompanied by his companions, managed to beat the demon king and bring peace to the world.  The years have passed and intoxicated by the atmosphere of peace that reigns, human beings have become weaker.  Fearing the fall of the human race 100 years later after the demon king's reincarnation, Ignir  decides to exile himself far from civilization in order to design a spell that will allow humans to win the next holy war.  However, the empire, fearing the dangers of its experiments, sent a troop of adventurers who, during a tough fight, put an end to the life of Ignir  Lamprok.  Thinking of dying, he wakes up five days later in front of a young demon who tells him that he is the demon king.  He therefore finds himself at the head of the completely weakened army of demons and having inherited the knowledge and power of the former demon king, he sets himself a goal, that of dominating the world in order to impose lasting peace.