Completing every job with ruthless accuracy, Train Heartnet is an infamous assassin with no regard for human life. Donning the moniker "Black Cat" in the underground world, the elite killer works for the powerful secret organization known only as Chronos. One gloomy night, the blasé gunman stumbles upon Saya Minatsuki, an enigmatic bounty hunter, and soon develops an odd friendship with her. Influenced by Saya's posi...