Title: ヴァンパイア十字界, Record of the Fallen Vampire
Author: Shirodaira Kyou (story), Kimura Yuri (art)
Genre: Shounen, Tragedy, Action, Drama, Supernatural, Romance, Sci-Fi, Fantasy
Serialized in: Square Enix Shounen Gan Gan
Total Volume Count: 9

Kenn's Comment: This ain't your Twilight. The main character goes through hell, and pretty much stays there, and you can't help but feel sorry for him. All the lemons that life gives him xD And you can't lemonade outta the lemons that life gave him. Almost every main character has some sort of tragic ordeal going on. It's awesome like that. Not overly depressing, but it ain't Yotsuba&. By the way, while it's a story about vampires, don't go in thinking about Twilight. These ain't your usual vamps.

Summary from MangaUpdates:
There is a legend that tells of how the world was almost destroyed thousands of years ago by the vampire queen after she unleashed her latent powers. Despite their efforts, the humans were unable to defeat her, and thus resorted to sealing her away until the time came that they would be powerful enough to destroy the seal and kill her. However, the humans are not the only ones after the seal. Having cast aside his kingdom and betraying his own race and the dhampirs (half-vampires), the vampire king is persistantly searching, even to this day, for where his queen has been sealed away so he may break the seal and free her before the humans do. Fearing that once the king and queen are reunited, they shall continue to destroy the world together, the humans and dhampirs hunt the king, using any method possible.