Black cat - Kentaro Yabuki

Train Heartnet, also known as "Black Cat," was an infamous assassin for a secret organization called Chronos...until he abandoned that cold-blooded existence to live on his own terms as an easygoing bounty hunter. But is Train's past as far behind him as he thinks?

Train's partner Sven is determined to rescue Eve, a girl-turned-bioweapon, from the dangerous arms dealers who are holding her captive. Sven and Train soon discover that the shadowy figure connected to this black market smuggling ring is none other than Train's mortal enemy, Creed. But why does Creed want to join forces with Train?