Tetragrammaton Labyrinth

Tetragrammaton Labyrinth (断罪者〜Tetragrammaton Labyrinth〜, Danzaisha Tetragrammaton Labyrinth) is a 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.

Plot
When darkness falls on the foggy streets of London, demons and monsters emerge to prey on human life. But demons aren't the only ones prowling the streets. Two women have picked up the fight as humanity’s front line defense against the darkness—a young gun-toting nun named Sister Meg and her mysterious, eternally youthful partner Angela. Together, they have made it their life’s work to spend their nights hunting the vile demons that stalk mankind.