Eirth, the son of the legendary hero who vanquished the Demon King, grapples with immense pressure to live up to his father's legacy. Feeling like a constant disappointment, Eirth stumbles upon the ghost of the Demon King, who offers to mentor him out of sheer boredom. Determined to prove himself, Eirth embarks on a unique training journey with his unlikely teacher. As he grows stronger under the guidance of his once-enemy, Eirth sets out to challenge both his parents' expectations and the world itself. Brace yourselves, for a new force is rising that will shake the foundations of past heroes, childhood friends, and the very essence of greatness.