As humanity revels in the hero's triumph over the Demon King, the inhabitants of the demon world gear up for a momentous event—the tournament that will determine the successor to the title of Demon King.
Fast forward three months, and the tournament unfolds with surprising ease, save for one peculiar detail—the frontrunner for the coveted position is none other than the human hero, Helck! With a cheerful smile and a wave, Helck effortlessly outshines his demonic rivals, all while vehemently expressing his disdain for humans. Though he calls for the annihilation of humanity, the true motives behind his seemingly cheerful demeanor remain shrouded in mystery.
With doubts clouding her perception of Helck's true intentions, Red Vamirio, one of the esteemed "Four Heavenly Kings" overseeing the demon realm, embarks on a quest to unravel the enigma surrounding the hero. As the title of "Demon King" hangs in the balance, the destiny of the demon world rests squarely on her shoulders.