GEKKI

Gekki summary:

In the Imperial capital of Tokyo, Tokito Tokitsukasa and his step-sister Kiriko are ordered to marry by their grandfather... but something isn't right. Kiriko can tell these people are keeping some secret from her... meanwhile, an infamous thief named Shiou escapes from the police in the night, only to run into a strange girl. And she looks just like Kiriko...
A 3-volume gothic horror series that centers around the tumultuous fate of a single girl!
From Manga Helpers