The hero Friede, a revered hero, was tasked with infiltrating hell. In doing so he was confronted by the demon lord Yurisha. Their battle concluded with the demise of both the hero and the demon lord. Immediately after, Fried was somehow revived as the new Demon lord. He is now tasked with defending the castle, and hell. Along the way he learns more about the demons he once fought. The former hero becomes the most powerful demon lord in history, his mission, to protect hell and save the demons who are in constant conflict with the humans