Black Cat

From OtakuWiki

Synopsis

Train Heartnet was originally an assassin working for an organization called Chronos, which ruled one third of the world's economy. Also named XIII, for the number carved on both his body and his gun – which was crafted with the legendary metal orichalcum, Train was possibly the deadliest – and most heartless assassin there was.

However, when he fails to make his mark, mostly because his target's child was on the scene, Train makes a chance encounter with Saya Minatsuki, a sweeper with as much skill with the gun as his, as well as an attitude that impresses the young assassin into leaving Chronos. However, this displeases an admirer of his, Creed Diskenth, who is convinced that Saya had bewitched Train, and plans to kill the girl.

It is two years later. Train is now a sweeper as well, partnered with Saya and Sven Vollfield, a sweeper with the ability to see several seconds into the future, as well as Eve, a biological weapon resembling a young girl. However, Train's past comes crashing back when Creed returns and kills Saya. Now Train is on a personal mission, seeking Creed in order to avenge Saya's death.