Why I Quit Being the Demon King

During an era of turmoil, the Demon King journeyed through 665 realms before invading the human realm. A courageous hero emerged to end the war, making a divine sacrifice that barely saved mankind. However, this sacrifice gave rise to a new Demon King – Demiourgos, the 666th. Surprisingly, he declared, "I quit being the Demon King," and left the demon realm. This is the tale of a renegade Demon King and a hero who becomes his subordinate. What led to the Demon King's unexpected resignation?