A spate of mafia assassinations occurs in America, the work of the mysterious organization named Inferno. "Phantom" is their most strongest and capable assassin, however a lone tourist witnesses Phantom's latest act of murder. He unwittingly exposes the top assassin's true identity, a young girl named Ein. Witnesses are usually killed, but the man is captured and taken to be brainwashed into "Zwei", Inferno's newest assassin, with no memory of who he is. From this point on, Zwei is drawn into a world of conspiracy, deceit and violence.
MAIN CHARACTERS
Zewei/Azuma Reiji

Ein
** Spoiler Alert!!! click to hide or show**
Claudia McCunnen

Lizzie Garland
Scythe Master

Isaac Wisemel

Raymond McGuire
Cal Devens

Godo Daisuke

Shiga Toru
Character of the Month:
Ein (Elen)
An assassin with such skill she was given the codename "Phantom", a designation given only to the best killer in Inferno. She was found by Scythe Master and was his first test subject to be given his assassin-processing treatment. She has no memories of her past and is incredibly apathetic. When she escapes to Japan, she changes her name to Elen and claims to be Reiji's twin sister. A long and rigorous investigation by Elen and Reiji traces her history back to Ulan Bator, Mongolia, and though the trail manages to stop there, Elen is able to find some peace in the area. In the OVA, she is shown to have an older brother, and it is suggested the village where she lived was massacred.
http://en.wikipedia.org/wiki/Phantom_~Requiem_for_the_Phantom~#Anime_series