Ao no Fuuin (Blue Seal)
I'd seen this mentioned as a classic story by Chie Shinohara, best known in the west for Red River and Mizu ni Sumu Hana, but I only just got around to tracking it down and am sorta glad I did. On the one hand, it's Darn Good Stuff -- on the other, I just lost a day when I needed to be doing other things, drat it. I intended to just check out the first chapter as I downloaded it for later reading -- my bad. It's been a while since I've been completely sucked into a story like that, and even longer since a supernatural suspense story did it for me.
The descriptions on Manga Updates and Storm in Heaven don't do the story justice, but it's the sort of wheels-within-wheels plot where anything more about the setup would be spoilery. It's not as sexy as Mizu ni Sumu Hana, but a lot bloodier.
SiH has the first eight (of 11) volumes for DDL and is actively working on the rest. Good stuff. Highly recommended, and specifically commended to anyone who thinks shoujo can't be as violent as seinen.
I remember reading this manga way back. Your right when you said it was gory.. but not as gory as most seinen but around there. The story was good up until about volume 7 or 8... I kinda gave up after that cause the story started going nowhere and real typical. And alot of stuff just didn't make sense.
One problem is the way the heroine either has or doesn't have a backbone depending on the needs of keeping the plot going. Around volume 6-7 this cause some major stupidities to happen -- in an annoying, rather than being in character, sort of way.
I still snorked it, though.