The term Ninjutsu is most commonly used to refer to the specific methods and techniques used by the Ninja. It translates as "the art of stealth." It began in an occupied Japanese territory 800 b.c. Those who practice Ninjutsu have said that their art is based upon a great Chinese military text, The Art of War, written by a general named Sun Tzu. This martial art is also associated with espionage and assassination, with little regard shown for the well-being of the assassin himself.

When feudal Japan collapsed, the remaining secret practitioners were absorbed into the Japanese Secret Service.

Disciples of Ninjutsu do not limit themselves to a few martial arts disciplines. Instead they study as many as they possibly can to become effective fighters. When students enter into the art of Ninjutsu, they are expected to train until they die. The Ninjutsu adhere to 18 disciplines, which were first stated in the scrolls of Togakure-ryü and which provide a complete training of the warrior in various fighting arts and complementary disciplines.

1. Seishin-teki kyöyö (spiritual refinement)
2. Taijutsu (unarmed combat)
3. Ninja ken (sword fighting)
4. Böjutsu (stick and staff fighting)
5. Shurikenjutsu (throwing blades)
6. Söjutsu (spear fighting)
7. Naginatajutsu (naginata fighting)
8. Kusarigama (chain and sickle weapon)
9. Kayakujutsu (fire and explosives)
10. Hensöjutsu (disguise and impersonation)
11. Shinobi-iri (stealth and infiltration methods)
12. Bajutsu (horsemanship)
13. Sui-ren (training in water)
14. Böryaku (military strategy)
15. Chöhö (espionage)
16. Intonjutsu (escaping and concealment)
17. Tenmon (meteorology)
18. Chi-mon (geography)