The hero Shio Hizaki, who once saved another world. After defeating the Demon King, he was forcibly sent back to modern times, but three years later, he is summoned again to stop the rampage of the secret organization “Helheim.” However, that organization is actually the embarrassing dark history he created during his first summoning, when he called himself the “Corpse King”! Who on earth is impersonating “Helheim” and spreading its notorious name? The Corpse King reunites his former strongest subordinate, “Hakkai,” and descends once more into another world to clear the organization’s tarnished reputation— all while cringing at his own dark past…