Yomigaeri no Maou

Yomigaeri no Maou summary:

Demon King Luruslia Nord; defeated by the hero, and someone who should have died. He had a number of things left undone, and a number of problems left unresolved, but following the slogan that ‘evil will be destroyed’, he should have disappeared. However, for some reason, he had miraculously gained a second life as a human. This details the life he leads from then on.