D.Gray-man, Vol. 1 is set in a fictional end of the 19th century England. The story follows a teenage boy named Allen Walker, who is cursed with a cross mark on his hand that transforms his arm into an enormous weapon. This weapon is used to hunt down and destroy akumas.

An akuma, generated by a 1,000-year-old phantom known as the Millennium Earl, is embedded into a human's soul during times of devastation and despair. The Millennium Earl uses these demons to fulfill his sinister goal: to annihilate all humankind.

Allen, a born exorcist, doesn't just destroy akumas; he can see the akuma hiding within a person's soul. Together with his fellow exorcists under the command of the Black Order, Allen leads the battle against the Millennium Earl, defending humanity from demonic forces.