Maoyu: Archenemy & Hero

まおゆう魔王勇者

The Hero storms into the Demon Queen's castle expecting a final battle, only to find her waiting with an argument instead of a sword. She explains that the ongoing war between humans and demons props up the human economy — ending it abruptly would collapse the Southern Nations, leaving hundreds of thousands to starve. Convinced by her reasoning, the Hero agrees to a secret alliance, and the two set out to reform agriculture, trade, and education across both realms while concealing their true identities.