Phantom -Requiem for the Phantom-

Reiji Azuma is an ordinary Japanese teenager who inadvertently becomes involved in a mafia assassination during his middle school graduation trip to Los Angeles, USA. Fortunately, because he was discovered to possess the talent of a killer, he was not silenced but had his memory erased and trained by Ein, the strongest female assassin in the organization, becoming the superhuman killing machine Zwei. After his debut, his career as an assassin seemed to go smoothly, but he was soon drawn into bloody struggles within the underworld. From then on, for the sake of his own future and that of his loved ones, Zwei must make various difficult choices.