Duffau is a duke in Pandemonium and as such has much power. He also gains the title of Pursuer as he hunts down the Sinners to restore the darkness to Pandemonium.

The year is 1928 A.D. The place is New York, U.S.A. The economic prosperity brought forth after the Great War also heightened the presence of something far darker and much more sinister: the demonic Sinners. The Magdalene Order is an organization that tries to counter this force. Two of its exorcists are Rosette Christopher and her assistant, Chrono. Both appear out of place in an organization like this, and they are in a quest to find Rosette's missing brother, Joshua. Their relationships, secrets and fates can only be revealed in time...
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(Source: Anime News Network)

[Wiki (jp)](https://ja.wikipedia.org/wiki/若本規夫)

Used to work for the Tokyo Metropolitan Police Department Riot Police.

America in the Roaring 20s. On the surface, it's a positive, peaceful time after the violence of the Great War. But lurking in the shadows is a dark element ready to snatch that peace away. Sister Rosette Christopher, an exorcist working as a part of the Magdala Order, has a duty to fight the demons which appear and cause destruction. But along with her companion Chrono, she usually ends up causing more destruction than the demons themselves! On one particular mission, they meet a young girl with a beautiful voice named Azmaria, who is being targeted by her own stepfather. As Rosette and Chrno work to save her, more is revealed about the relationship between them. There is more to these two than meets the eye.<br><br>

(Source: ADV)

Koushaku Duffau