Zwei(Reiji Azuma,Ein(Erin)

Zwei (Reiji Azuma)
The title character of the story, Zwei was a perfectly ordinary tourist from Japan, before witnessing an Inferno assassination in America and being kidnapped. He was able to elude his pursuers long enough for them to realize he had a natural survival instinct that was perfect for an assassin. He had his memory erased through a combination of drug and hypnotherapy. And thus became the second generation Phantom. The name Zwei is simply a code name to show he is the second experimental assassin created by Scythe Master. Through Claudia, one of the three top executives of Inferno, Zwei is able to learn his true identity as Reiji Azuma. When he returns to Japan, he goes back to using this name. When his killing intent shows, in the anime, his eyes turn green with orange in the center.
Game: Voiced by: Kōsuke Okano
OVA: Voiced by: Takahiro Sakurai (Japanese), David Keefir (English)
Anime: Voiced by: Miyu Irino

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.
Game: Voiced by: Omi Minami
OVA: Voiced by: Omi Minami (Japanese), Mela Lee (English)
Anime: Voiced by: Ayahi Takagaki