In an alternate world, King Albert of Elfrieden and Prime Minister Marx decide to summon a hero to face a dire threat. Kazuya Souma, a young man training to be a civil servant, finds himself summoned as their hero. Albert and Marx explain demons appeared 10 years ago and took over the northern kingdoms. The remaining kingdoms keep them invading, but maintaining armies is expensive, so Kazuya was summoned by the bankrupt Elfrieden Kingdom to trade to the Gran-Chaos Kingdom instead of gold. Kazuya convinces Albert to keep him as he was training to be a civil servant...