Allen Walker is a 15-year old kid whose left arm can transform into a monstrous claw and destroy Akumas, evolving machines created by The Earl of Millennium to help him destroy humanity. He got trained by one of the Black Order generals Cross Marian which he told him that he can become an Exorcist, humans who can destroy Akuma, for the Black Order, an organization attempting to stop the Earl. Allen became a powerful asset for the organization because he can detect disguised Akuma's with his Cursed Eye. During his battle, Allen meets others exorcists namely Lenalee Lee a young chinese girl, Yu Kanda a japanese swordsman and Lavi heir of the Bookman Clan and makes many friends. But The Earl gathes the Noah Family superhuman descendants of Noah who can destroy Innocence. Both side start to make their search for the Heart the most powerful piece of Innocence that will ensure victory to the side that finds it.