Spying in Japan dates as far back as Prince Shōtoku, although the origins of the Ninja era date much earlier. Ninjutsu was developed by various groups of people mainly from the Iga and Kōka regions of Japan. Throughout history the shinobi have been seen as assassins, scouts and spies. They are mainly noted for their use of stealth and deception. Throughout history many different schools Katana have taught their unique versions of ninjutsu. An example of these is the Togakure-ryū. This ryū was developed after a defeated samurai warrior called Daisuke Togakure escaped to the region of Iga. Later he came in contact with the warrior-monk Kain Doshi who taught him a new way of viewing life and the means of survival (ninjutsu).
Ninjutsu was developed as a collection of fundamental survivalist techniques in the warring states of Feudal Japan. The ninja used their art to ensure their survival in a time of violent political turmoil. Ninjutsu included methods of gathering information, and techniques of non-detection, avoidance, and misdirection. Ninjutsu can also involve training in free running, disguise, escape, concealment, archery, archery, and so on.
Skills relating to espionage and assassination were highly useful to warring factions in feudal Japan. These persons were literally called "non-humans" (非人, hinin). At some point the skills of espionage became known collectively as ninjutsu, and the people who specialized in these tasks were called shinobi no mono.
- Seishinteki kyōyō – spiritual refinement
- Taijutsu – unarmed combat
- Kenjutsu – sword techniques
- Bōjutsu – stick and staff techniques
- Sōjutsu – spear techniques
- Naginatajutsu – naginata techniques
- Kusarigamajutsu – kusarigama techniques
- Shurikenjutsu – throwing star techniques
- Kayakujutsu – pyrotechnics
- Hensōjutsu – disguise and impersonation
- Shinobi-iri – stealth and entering methods
- Bajutsu – horsemanship
- Sui-ren – water training
- Bōryaku – tactics
- Chōhō – espionage
- Intonjutsu – escaping and concealment
- Tenmon – meteorology
- Chi-mon – geography
- The six pillars of ninjutsu are: spirit, weapons, wisdom, strength, power, and stealth.
- Sun Tzu praised the importance of spies and assassins in his book The Art of War.
- Ninjutsu is often rendered as ninjitsu within TMNT media, because of an old mistaken romanization of the word from its original Japanese language.