The loss of a loved one can be excruciating, making one yearn to bring them back to life, but the Millennium Earl takes advantage of this vulnerability. He employs departed souls to create his lethal mechanical weapons, namely the "Akuma." These devices are a dreadful trap for souls, as they remain imprisoned forever with the only solution being the use of the "Innocence," an Anti-Akuma weapon. After three years of instruction under General Cross, Allen Walker is assigned to the Black Order. This organization's mission is to fight the Akuma and the Millennium Earl, and Allen must become an accredited Exorcist. His cursed arm and eye harbor his Innocence, allowing Allen to detect the suffering souls imprisoned in these dreadful weapons. Together with his fellow Exorcists, Allen attempts to thwart the Millennium Earl's alarming plots that may bring about the world's demise.