Black Cat

Black Cat is about a former assassin named Train Heartnet who used to work for Chronos. He is a master of gun and used to be a cold blooded killer with number 13 in roman numeral on his left chest. After meeting with a bounty hunter named Saya, Train turn into a loving person and become a sweeper or bounty hunter. Together with his partner Sven and a mysterious girl named Eve, they travel to hunt wanted criminal. The series has 24 episodes and I think it's interesting but I recommend this for teens to watch.