Plot Summary: A group of assasins are controled by Chronos. They all have a number on their neck. But number 13 which is Black Cat has the characteristics of a cat, because a witch cursed him. He is supposed to kill people but he also hates the thought of killing people. The world is secretly controlled by a secret organizition, Chronos. Under the command of this mysterious organization, are the Chronos Numbers, a group of powerful assasins, taking orders to eliminate certain target secretly to keep the so-called ‘peace’. One of the most powerful is the Number XIII, Train Hartnett, or known as Black Cat. At first he seems to be a cruel killer, a meeting with a girl Sweeper changed him completely. Now as a Sweeper, train travelled with his partner Sven Volfied to hunt down criminals. Train Heartnet is known as the Black Cat for his quick reactions to attacks and his title as Number Thirteen as member of the secret society Chronos. He is an unbeatable master gunman, a cold and unfeeling killer until he meets Saya, a bounty hunter, or “sweeper”. She teaches him the value of a human life, and that one should live in order to repent for one’s mistakes rather than die because of them. Through her, Train learns to love and care for other people as he too becomes a sweeper and travels with his partner Sven and the mysterious girl Eve.