Ninjas or shinobi ("to sneak”) have become kings of popular culture and their acrobatic trained-killer antics have been featured in hundreds of movies and television series. These deadly mercenary spies of the Sengoku period in 15th century feudal Japan were highly skilled in espionage, sabotage, infiltration, assassination and guerrilla warfare. But underlying their weapons and combat training, an ancient set of nine secret hand signs were believed to make ninjas - super ninjas!

During the social unrest of the 15th-17th century ninjas were active in the Iga Provence, especially in clans around the village of Kōga. Here, ninja masters compiled shinobi manuals based on Chinese military philosophy, most notably the Bansenshukai (1676). By the time of the 1868 Meiji Restoration, the skills of the shinobi killers were no longer required and they became a thing of myth, legend and folklore and it was around this time these clandestine warriors were first given the abilities of invisibility, walking on water and control over the natural elements.

Roof-top ninja (Agustin Rafael Reyes / flickr)

Among the factual stories of the original ninjas is the tale Yagyū Munetoshi (1529–1606), a renowned swordsman of the Shinkage-ryū school’s grandson, Jubei Muneyoshi, told tales of his grandfather's status as a ninja. And, Hattori Hanzō (1542–1596) was a legendary samurai warrior from the Iga province, and the ninjutsu manuals which were subsequently published by his descendants have led many Japanese historians to define him as a “ninja master.”

The Nine Symbolic Cuts

Several ninja traditions have been preserved in popular culture, but none is so deeply-mystical and misunderstood as Ku-ji meaning “nine symbolic cuts”. Kuji (九字) means nine symbols, and Kiri (切) refers to the cutting motion. The nine symbols are named: rin, pyo, to, sha, kai, jin, retsu, zai and zen. Some experts believe this secret system of mantras was developed it China, but others insist it emanated from Vedic India. Others argue it comes from mikkyo (Japanese esoteric Buddhism), while in South Asia it is believed to be of Taoist origin, not Buddhist. Notwithstanding these differing points of view, practice of Kuji is found extensively in Shugendō, the ascetic mountain tradition of Japan, and ryobu Shinto, which is a union of Buddhist and Shinto beliefs. Therefore, it is highly likely this is the original source of the secret hand signs.

Ku-ji “nine symbolic cuts” (public domain)

Kuji. Science or Something Else?

It is well documented that ninjas used Kuji-Kiri to induce specific states of mind which helped them function under extreme stress. Each of the nine symbols was believed to invoke/awake the energies associated with specific abilities, for example, say a ninja had been staking out an assassination target by hiding underwater for three days. When the target finally arrived, to exit his deep meditative state, the ninja night perform the hand symbol 在/Zai: “take position.”

Stripping away the layers of supernatural notions associated with Kuji-Kiri, it is essentially a meditative process accompanied by hand signs, controlled breathing and visualization process. Together, these activities induce powerful mental states and it could also be argued that this entire process was a form of self hypnosis, which induced the reported physical changes. To get to the bottom of the thousands of reports of unexplainable ‘mind-body’ interactions, in 2012 the Mie University (School of Medicine) in Tsu City, Japan, studied the effects of Kuji-Kiri across a section of 15 “ninja professionals.”

The first part of this fascinating experiment monitored the ninjas brainwaves and heart rates before and after performing Kuji-Kiri. Each of the 15 ninjas increased their alpha-2 brainwaves, enhancing awareness and relaxation, and they all reduced beta waves which cause annoyance and anxiety. They also decreased production of theta waves which are produced in deep relaxation and sleep states. The second experiment compared the fight-or-flight response of the 15 ninjas before and after the practice of Kuji-Kiri and it monitored that all 15 ninjas “heightened their levels of alpha-2 waves and dropped their Beta waves significantly”. When these results are presented beside the brainwave patterns of deep state mediators, the results are striking.