Cartagra: Affliction of the Soul is an adult visual novel set four years before the events of Kara no Shoujo. The game has you playing as Takashiro Shugo as he investigates a serial killer murdering prostitutes in Ueno, and MangaGamer released a demo for it this morning.
The Cartagra demo can be downloaded on this page (NSFW). The full game will cost $34.95 when it is released, although MangaGamer haven’t announced a release date for it yet.
Meanwhile, MangaGamer are also in the process of localizing Kara no Shoujo 2, a sequel to the first game.