We meet 87-year-old grandmaster Masaaki Hatsumi, living legend of the ninja arts, and speak with one of his instructors, an American living in Japan who has reached a high level of proficiency in ninjutsu. Keeping the secretive techniques of the ninja alive in the modern age, Hatsumi sensei has attracted countless thousands of students from around the world, even winning recognition from law-enforcement agencies such as the FBI. We explore the history of the ninja arts and their enduring legacy.