Towards the end of the 19th century, Allen Walker officially joins the organization of Exorcists that destroy the beings known as Akuma; mechanic weapons made by the Millennium Earl with the suffering souls of the dead. Allen has both a cursed eye and an anti-Akuma weapon as an arm, bearing the power of 'Innocence,' a gift given to him as an apostle of God. Allen, along with his fellow Exorcists must put a stop to the Millennium Earl's ultimate plot that could lead to the destruction of the world and all who live on it.
In Victorian era Europe, a young boy loses everything he once held near and dear to a vicious plot. In his moment of death, he strikes a deal with a demon: his soul, in exchange for revenge. Ciel Phantomhive is now the head of the Phantomhive corporation, handling all business affairs as well as the underground work for the Queen of England. His new partner is a demon butler, Sebastian Michaelis, whose prowess as a butler is only surpassed by his strength as a demon.
The story follows the `strongest juvenile delinquent,` Oga Tatsumi, a first year in `Ishiyama High` the school for delinquents. One day while sleeping next to a river he sees a man floating down it, he pulls him to shore and the man splits in half revealing a baby boy. This boy is the son of the demon king and he has been chosen as the one to raise it with the baby`s demon maid Hilda. The story follows his life with the child and at the delinquent school.
This world consists of two dimensions joined as one, like a mirror. The first is the world in which the humans live, Assiah. The other is the world of demons, Gehenna. Ordinarily, travel between the two, and indeed any kind of contact between the two, is impossible. However the demons can pass over into this world by possessing anything that exist within it. Satan the god of demons, but there`s one thing that he doesn`t have, and that`s a substance in the human world that is powerful enough to contain him!!