Black Blood Brothers

Saya Otonashi, a seemingly normal high school student, suffers from amnesia and she can't remember the past year of her life. One day, after a man appears and gives her a katana sword, her destiny begins to be revealed. Soon she finds herself fighting the latest threat to humanity - Chiropteran monsters, ravenous immortal creatures that can change their form, disguising themselves as human beings. They feed off blood and hide themselves within the human world. An organization known as the Red Shield has been waging a private war to wipe them out and now the struggle has grown. Saya's journey for the truth has begun.

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, the Vatican has to rely on other allies to counter the situation. The protagonist, Abel Nightroad, is a traveling priest from the Vatican and a crusnik, a vampire that drinks the blood of vampires. He is a member of the "Ax", a special operations group led by Cardinal Catherina Sforza. He encounters a young girl called Esther, who decides to go with him to Rome and train at the Vatican. Soon after he meets her, the order of Rozencreuz, led by Abel's twin, Cain, tries to continue the war so they can rule the world. It's up to Abel and the AX to try and stop them.

The story revolves around Blade, a "Daywalker" vampire hunter who was born with vampire and human blood after a vampire attacked his mother. While visiting Japan on a mission, Blade tracks down Deacon Frost, the vampire who killed his mother. Blade confronts "Existence," a mysterious organization composed of vampires modified by Frost.

Staz is the vampire boss of a section of the demon world, but he has little interest in human blood. He's more infatuated with Japanese culture. When he learns that Yanagi Fuyumi, a Japanese teenage girl, accidentally wanders into the demon city, he jumps to the occasion. However, while Staz deals with an intruder on his turf, the oblivious Fuyumi is killed by a monster and becomes a wandering ghost. The disappointed Staz vows to her that he will find a way to bring Fuyumi back to life.