Yuki Yonai

The Third World War (2099–2126) devastated part of the Earth. Former nations are reforming while new powers emerge, and groups of humans struggle to survive in ruined cities. The story follows Deunan Knute and her partner Briareos as they search for the legendary city of Olympus.

The devil king Lucifero suddenly declares he's going to retire, and must choose a successor. The Devil King Cadets gather one after another, and go to the human world to participate in the succession contest. But only the devil king's own descendant Osamu has no interest whatsoever in the contest. Compared to the fate of the world, Osamu is more interested in his part-time job at a convenience store. Osamu has no choice, however, but to start collecting familiars called "Child," which are born from human souls. Osamu still only has an interest in his part-time job, and he's a few steps behind the rest of the Cadets.