9 Banme no Musashi

The “ultra secret” organization, Ultimate Blue, dedicates itself to fighting terrorists and criminals in the name of peace. Their top agent goes by the code name “Musashi #9;” she is a quiet yet fearless 16 year old girl.
From Baka-Updates:
Exotic. Smart. Lethal. Musashi #9 doesn’t live the life of a normal teenager. Hers is full of intrigue, violence, and death.
Some people want to change the world. This sixteen year-old girl can. Deep ideological, religious, and social differences drive the world closer to destruction, and the innocent masses suffer while politicians huddle in safety. One ultra-secret organization is committed to preserving world peace, and their top agent goes by the code name Musashi #9. This agent battles terrorists and extremists, while bringing hope to the people she saves. The world may be a dangerous place, but it’s a whole lot safer with Musashi #9 in it.