The Demon King has been slain by the Hero of Sylvennian Kingdom. However, the main protagonist, would not expect his death as he headed home from their Demon King's expedition. Trialed and executed as a Demon King, despite that he had slain the kingdom's enemy, their kingdom and the Hero Party betrayed the hero. The summoned hero had left his soul with nothing but hatred and revenge.

Regaining back his memories from his two previous lives in purgatory, the main protagonist had realized how much of a tool he was used in the kingdom, and how much potential is wasted in this world where magic runs in every being's blood.

Since the defeat of Demon King, the Sylvennian Kingdom had been one of the nations who hold the right to lead other nations. But with their influence, their corruption has been seeded to other nations as well. It is a matter of time before nations will start a war. Summoned heroes that are previously used for slaying the Demon King became pawns that fight for war. Other kingdoms had their own summoned heroes as well as they train them for an upcoming war.

Reincarnated in a small kingdom called Alimanya, a nation in constant war against its own people, the MC will use his knowledge to turn this run-down nation into a prosperous Empire.