The Demon King's Friend

After a hundred years of war between humanity and demons, the hero Part and imperial mage Noah are sent to activate the Continental Demon-Sealing Formation. It is humanity's last plan to make the demons disappear. At the final destination, they meet a young shepherd named Roro, who accompanies them as the mission nears completion. Then, on the day the formation is meant to end the war, everything changes. The story begins where a straightforward victory over the Demon King was supposed to happen.