Phantom The Animation
English name: Phantom: The Animation
Genres: Action, Drama
Type: OVA, Episodes: 3
Aired: Feb 27, 2004 to Nov 26, 2004
Studio: Arcs Create
Source: Visual novel
Rating: R - 17+ (violence & profanity)
Synopsis:
Zwei was an ordinary person, until one day, while walking the streets a night, he witnessed a brutal assassination. He managed to avoid the sniper, a young girl named Ein, but was soon captured, and had the memories of his former life erased. He is spared death only by accepting a condition: to train to become an assassin alongside Ein. Now, he must find a way to free himself from this shady world and reclaim his life once again.

(Source: ANN)