When his terrible scum of a father died, they mysteriously left him 500 million yen. The young boy quickly decideds to live as he please from now and gets completely absorbed by the super difficult online game “Dungeon Attack”, where he is the first player ever to defeat all 72 demon lords. But after completing the game and answering a mysterious question, he gets forcefully teleported to the game world and unbelievably reincarnates as the rank 71 demon king, the weakest and lowly “Dantalian”! In this story of reversals and revenge, our protagonist trusts only his memory of defeating the strongest demon king and his silver tongue to survive the incredibly cruel world he finds himself in.