Maoyuu Maou Yuusha

The Hero reaches the Demon Queen's castle expecting a final battle. Instead, she asks him to consider what victory would actually bring: economies built on conflict could collapse, leaving hunger and new wars in its place.

They form an unlikely alliance to change the conditions that keep humans and demons fighting. Agriculture, trade, and education become tools as important as a sword, but challenging the interests sustained by war proves harder than defeating a single enemy.