Trinity Blood

The background is in the distant future after the destruction brought about by Armageddon. The war between the vampires and the humans continue to persist. In order to protect the humans from the vampires, Vatican has to rely on other allies to counter the situation. The protagonist, a priest called Peter Abel Nightroad, travels through the countries as a representative for the Vaticans. However, he is also part of "Ax", a special operations group controlled by the Cardinal Catherina. His encounter with a young girl called Esther will determine the struggle and survival between the human race and the vampires.

Synopsis from Anime News Network