"Regain the true power by regaining the shattered sign of the Demon King."
The Demon King who once reigned as the King of the Demon World and challenged the battle to the heavens. He was defeated after a deadly battle with the angels, and the "sign" that was the source of his power was shattered. The "sign" was divided by the six angels of the heavenly army, and he was managed so that he would never wake up again. Only one piece of the "sign" disappeared somewhere, and the destination became unknown.
Ryuga Sada is a human being born from the "fragment of the sign" whose destination is unknown. He once regained his memory of the past and remembers reigning as the Demon King.
And he began his actions to regain the "sign" that was the source of his robbed power in order to challenge the heavens again.
