This is a fantasy story written in 2001 by Jacqueline Carey. Recently, it has been translated into Japanese and published here.
When I started reading, I thought I had bought the wrong book as the heroine was a courtesan. Reading further, I discovered that the story seemed to be about conspiracies in an aristocratic society. I can’t be absolutely certain because the first volume was divided in three parts, and currently only the first third has been translated into Japanese. Even so, the story is interesting.
I want to read the next one soon, but I don’t know when the other two parts will be released. I seem to need to read it in English, but it would be too difficult to read the story in it's original English language as there are too many coined words and "specialized" terms for physical pleasures. Therefore, the Japanese translation is more preferable as these terms have been translated into words more easily understood by Japanese readers.
Regardless, the amazing part of the story is the elimination of Christian morals. Japanese people originally don’t hold to the same kind of morals, so those who grew up in a Christian community would feel the story is more specific or unique than I do.
Koir, thanks for correcting my English.