Set in a fictional 19th century England, D.Gray-man is the story of Allen Walker, a 15-year-old boy who roams the earth in search of Innocence. Washed away to unknown parts of the world after The Great Flood, Innocence is the mysterious substance used to create weapons that obliterate demons known as akuma.

Following a brutal battle with a Level 4 akuma, Allen seems to be undergoing an odd and disturbing change. Meanwhile, a new breed of Exorcist is introduced at Black Order headquarters and, at Asia Branch, Kanda learns some disturbing things about his own status in the Black Order's Exorcist operations. Needless to say, Allen and his friends are ill prepared to deal with the simultaneous appearance of the servants of the Millennium Earl all over the world!