Kunoichi - Ninja Girl
Kunoichi(くノ一) is the female term for ninja. It actually means Dragon Lady and was the name given to women of the Black Dragon Fighting Society.
Story has it that There was once a daughter of a Japanese lord who had been assassinated. She was subsequently married off to a new husband. One night she invited all the friends and relatives of her new spouse to a feast and poisoned them. This left her with a reputation for ruthless efficiency.