Oono Akira is an average guy working for a company that's creating a new video game. He often plays as his character Maou (Dark Lord) while working on the game, but one day when he goes to log in he's suddenly transported into the game's world! To make matters worse, in-game characters begin traveling from far and wide to defeat him. He soon happens upon a young villager named Aku whom he saves from being sacrificed. Together with Aku, Mao begins stirring up trouble wherever he goes!