Towards the end of the 19th century, Allen Walker officially joins the organization of Exorcists that destroy the beings known as Akuma; mechanic weapons made by the Millennium Earl with the suffering souls of the dead. Allen has both a cursed eye and an anti-Akuma weapon as an arm, bearing the power of "Innocence", a gift given to him as an apostle of God. Allen, along with his fellow Exorcists must put a stop to the Millennium Earl's ultimate plot that could lead to the destruction of the world and all who live on it.