Tetragrammaton Labyrinth

 is a Japanese manga series written and illustrated by Ei Itou. The manga was serialized in the Japanese "seinen" manga magazine "Comic Gum" between January 26, 2005 and November 26, 2007, published by Wani Books. The manga has been licensed by Los Angeles-based company Seven Seas Entertainment for distribution in the English language. The first English-bound volume was released on June 30, 2007 with the second and third being released on November 28, 2007 and July 8, 2008, respectively. The fourth volume was released in December 2008.
Plot.
Tetragrammaton Labyrinth is set in alternate c.1900 industrial London, wherein Scotland Yard doesn't interfere with Meg Cross, a nun with a special talent in exorcism, and her eternally youthful partner Angela who deal with extraordinary crimes. To keep mankind safe from the creatures that lurk in the shadows Meg and Angela continue to exterminate demons and bring demon summoners to justice.