Darkness is moving in, and young exorcist Allen Walker is humanity’s greatest hope against the wicked forces conspiring to bring civilization to its knees. Akuma – cruel spirits born of tragedy and lost souls – lurk in every shadow, willing and eager to do the bidding of their leader, the dread Millennium Earl. With an eye cursed to see evil in its truest form and blessed with an arm to slay soul-devouring demons, Allen stands ready to confront the gathering evil. Should he fail, Innocence will be lost forever. The war to decide the fate of mankind has begun – and the carnage will be endless.

In the beginning, an "orb" is cast unto Earth. "It" can do two things: change into the form of the thing that stimulates "it"; and come back to life after death. "It" morphs from orb to rock, then to wolf, and finally to boy, but roams about like a newborn who knows nothing. As a boy, "it" becomes Fushi. Through encounters with human kindness, Fushi not only gains survival skills, but grows as a "person". But his journey is darkened by the inexplicable and destructive enemy Nokker, as well as cruel partings with the people he loves.

Guts, a man who calls himself "The Black Swordsman", looks back upon his days serving as a member of a group of mercenaries. Led by an ambitious, ruthless, and intelligent man named Griffith, together they battle their way into the royal court, and are forced into a fate that changes their lives.

Allen Walker is an exorcist working for the Black Order whose mission is to protect mankind from the evil Millennium Earl and his deadly Akuma. Allen and his comrades must recover lost Innocence while defending against the Earl’s terrifying army. But if they fail, Innocence will be lost forever.