Yomigaeri no Maou

Demon King Lurusliana 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.

(Source: Oniichanyamete)