Trinity Blood (トリニティ・ブラッド)

Trinity Blood (トリニティ・ブラッド Toriniti Buraddo) is a series of Japanese light novels written by Sunao Yoshida with illustrations by Thores Shibamoto and originally serialized in The Sneaker. Set 900 years after an apocalyptic war between humans and vampires, the series focuses on the on-going cold war between the Vatican and the Empire. Fighting on the Vatican's side is Abel Nightroad, a Crusnik which feeds on vampires. A blend of sci-fi, fantasy, and political intrigue, as some in the Vatican and the Empire strive for peace, other factions will do anything to stop it.
Trinity Blood has been adapted into both manga and anime series, with continuity differences between the three versions. After Yoshida's untimely death on July 15, 2004, Kentaro Yasui, his friend and the author of Ragnarok novels, stepped in to complete the remaining novels. Yasui also aided in completing the manga, with illustrations by Kiyo Kūjō. The anime series, spanning 24 episodes, was produced by Gonzo and originally aired on WOWOW network.
When Earth's population drastically increased, humanity led by the United Nations attempted to colonize Mars. During the colonization, they discovered two alien technologies: the Bacillus and the Crusnik nanomachines. The colonists installed the Bacillus in their bodies which transformed them into Methuselahs. They installed the Crusnik in the bodies of four test tube babies: Seth, Cain, Abel and Lilith whose enhanced bodies were the only ones able to survive the procedure.
Continuing wars on Earth eventually led to "Armageddon", the apocalyptic event that happened 900 years before the start of the story, and the colonists returned to Earth to help with rebuilding, but when the colonists returned to Earth, a war broke out between the Methuselahs and the humans who had remained on earth. Abel, Cain, and Seth took the Methuselah's side—while Lilith supported the Vatican, which guarded humanity. During the war, Cain went insane and killed Lilith. In grief, Abel took her body to the Vatican where she was buried. Abel remained at her side, weeping for her, for 900 years.

# Reference
http://en.wikipedia.org/wiki/Trinity_Blood
Trinity Blood Box Set(Amazon.com)