D. Gray Man

A young man named Allen Walker becomes an exorcist who can see the souls of demons due to his cursed eye. He goes to the black order to be encountered with both enemies and allies. His allies, are his fellow exorcists, who, just like him, each own something called "an innocence” which is like an anti akuma (demon) weapon. The exorcist’s enemy is non-other than the Millennium Earl, who is the creators of the demons. He creates those demons from the sadness of human beings. Allen’s past is a mystery even he himself doesn’t know about. The rest, you shall watch and find out for now. =]