Maoyuu Maou Yuusha

In Maoyuu Maou Yuusha, fifteen years after the war between humans and demons began, the Hero grows frustrated with the slow advance into the Demon Realm and leaves his companions behind to race toward the Demon Queen's castle. When he finally reaches her palace, he expects a final battle and instead finds a queen of unmatched beauty who asks for his help. The Hero refuses at first, insisting that the conflict is devastating the Southern Nations rather than solving anything. The Demon Queen counters with a hard truth: the war has also united humanity, strengthened trade, and brought wealth and prosperity, and she presents evidence to support her claims. She warns that if the fighting ends too abruptly, the supplies sent by the Central Nations to aid the Southern Nations will stop, and hundreds of thousands could starve. With that in mind, she offers the Hero a plan to end the war while bringing hope to the Southern Nations and to the rest of the world, but she needs his help to make it happen. Convinced, the Hero agrees to join his former enemy, and the two set out for the human world, bound to stay together through sickness and health as they try to reshape a conflict that has consumed both races.