The series is set in a fictional world at the end of the 19th century and stars Allen Walker , who joins the Black Order of Exorcists . Using an ancient power called Innocence , he goes into battle with the Thousand-Year-Old Count and his army of demons, who aim to destroy humanity. Hosino lifted most of the characters from his previous works and drawings , such as Zoneor Continue . The series is known for its dark history, there was one instance where Hosino had to rewrite a scene because he found it too violent for his young readers.