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.

Teen exorcist Allen Walker is given his first assignment, and his perilous mission takes him to southern Italy, where an Innocence has been located. Along with fellow exorcist Kanda, and Tom, a "finder"--one of a support group for exorcists--Allen must vanquish the akuma that covets the Innocence.