The Great Tiger Kingdom of Haan, the Gran Chaos Empire, and the Maritime Alliance headed by the Kingdom of Friedonia compete with one another in a newly tripolar world.
Suddenly, the Spirit Kingdom of Garlan, home to the high elves, attempts to make contact with these three great powers. They desire to regain the land they lost in the expansion of the Demon Lord's Domain. Souma, however, refuses to help them, seeing no benefit in doing so. Meanwhile, the Great Tiger Kingdom accepts their request and sends troops.
Things soon take a downturn as a crisis unfolds; healthy soldiers are collapsing one after another. It turns out that a deadly disease known as the Spirit King's Curse has been running rampant in the Spirit Kingdom! In the face of a novel disease that could threaten the whole world, Souma introduces new policies no one has ever seen before!