Under Ninja, Volume 2 (manga)

Now armed with modern ninja gear, Kudo begins to test out his new tool set throughout the mean streets of Tokyo. Unbeknownst to him, there is a Russian agent in town set on disrupting Japan's ninja corps. While still fresh and not yet fully trained, Kudo is put on alert to take care of a terrorist in the city.

It just so happens that this agent also happens to possess ninja skills!