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To Ensnare Enemies, Ninjas Used Mind Games — and Scuba Tanks




The newest book by renowned ninja researcher Dr Atsumi Nakajima, 73, from Yamaguchi Prefecture, reveals previously unknown ninja tools (ningu), secrets of the ninja arts, and methods of use. What is the significance of some of the more uniquely named items?


By Atsumi Nakajima
223 pages
The Science of Ninja (Yousensha Publishing, Only in Japanese)


Moreover, in a single stroke, he details how ninja ingeniously used human psychology in their intelligence gathering methods and the daily lives of ninjas which they themselves never revealed.


Ninja Scuba Tank: The Breath-Bag


Najkajima has published a modern Japanese translation of the Bansenshukai, which details the ninja arts of both the Iga and Koga regions.



The diving apparatus, “Breath Bag,” which does not appear in the Bansenshukai, was first revealed in 2016 in Nakajima’s history book, The Science of Ninja (Yousensha Publishing). It has a unique shape: an oval bag with three hoses exiting from the top, and strings attached to the middle and bottom of the bag.


According to Nakajima, the records of the breath bag were found in an old text from the Edo Period, “The Secrets of the Ninja (Shinobi no Hisho).” Although Nakajima accumulated a range of old texts, unfortunately none of them contain details of the year of production, nor the region where it was used.  


The breath bag, used for swimming underwater, was filled with air and was carried on one’s abdomen. Of the three hoses exiting the top of the bag, two were inserted into the nose, while the remaining hose went in the mouth. Air from inside the bag was drawn in through the mouth hose, and expelled via the nose hoses. It is thought that it would allow for movement without bubbles reaching the water’s surface.


Although the concept of a ninja underwater using a straw to breathe has been featured on television and the like, “There were times when the enemy had also hired ninja or possessed knowledge of ninja arts, so it was dangerous, as one could be discovered when hiding in the shadows using a straw,” Nakajima explained.


In that respect, the underwater breath-bag was harder to detect.



So, what were the ninja doing underwater, using this breath-bag?


In the “The Secrets of the Ninja,” there is a record of “going to cut the anchor line of an enemy’s boat.” Nakajima said, “It is plausible that ninja would attach a key-shaped tool to an opponent’s small boat, overturn it, and run away.”


The strings in the middle and at the bottom of the bag were used to attach the breath-bag to the ninja’s body. However, it seems that the breath-bag was not used in all situations, as it was written, “Do not use in rough conditions.” One can assume that these kinds of warnings were written because it was meant to be actually used.



Flipping an Enemy: ‘The Worm Technique’



In Nakajima’s new book Ninja Tactics: Reading the Secret Manuals (Kadokawa Sophia Bunko), published in 2016, he explains the lifestyle and various ninja arts of the Kishuu Ninja School as outlined in the secret, Edo Period ninja manual “True Path of the Ninja (Shoninki).”


One of the more brutal examples is the “Worm Technique,” used to turn adversaries into allies. The worm, which “lives in the stomach of the enemy and devours their body,” refers to the tapeworm.


Firstly in (1) it explains how to befriend an enemy’s servant. Eight examples of suitable targets are given, including: one who has committed a sin against their ancestors, one who holds a grudge against their lord, one who receives a low stipend despite their loyalty and ambition, one who thinks their lord a fool, one who has difficulty with their general, someone of low rank, someone with a strong desire for money or status, a two-faced person, and so forth.


The method used to turn these targets is outlined in (2), and it is disturbing. Disguise yourself as a rich, masterless samurai (Ronin), acquaint yourself with the target, deepen the friendship, ascertain their thoughts, pick your time carefully to share confidences, and offer favorable terms…. The next step is to confirm the agreement (create a contract). However, when doing so, one should make the promise on the understanding that “a family member is being held hostage,” as written in the manual.


It’s quite a brutal method. Additionally, there is also content which states that “humans are beings which will betray their loyalty for greed and lust,” illustrating the level of skill the ninja had in being able to read the heart, and prey on those weaknesses.



Did ninja ever actually use such skills? Nakajima, deals with this point, referring to a record detailing the activities of a shogunate spy from 1628 (5th year of Kanei, during the Edo period), when he searched “Sanuki, Iyo, Tosa, Awa” (Modern-day Shikoku), conducting an investigation of Tokushima Castle and the surrounding town.


The research materials were from a former house of the Mizuguchi Clan and donated to Mizuguchi Town, prior to the amalgamation with Koga-Shi, Shiga Prefecture. Accordingly, as Nakajima explains, “It is plausible that the spy was a Koga Ninja, which would make it possible to learn about the actual content and methods of their work.”


It is not only the dimensions of the castle and location of the gates which are noted, but also the local townscape, position of the sandbars, and also the locations of the homes of samurai in so-called “Samurai Towns,” were carefully researched and recorded.


In addition, the names of 48 samurai, including “Inada Shuri” and “Kashima Mondo,” were listed, along with their stipends, current circumstances, and position.


Especially with respect to the detailed descriptions of the samurai, Nakajima said, “Gathering information on important figures, and identifying which target to use is the most important part.” It is conceivable that, should the need arise, the Worm Technique could then be used to turn an enemy.



Given that it was collated in less than half a month, the records also contain a remarkable variety of information, such as noting the number of horses at “around 600 animals,” and the number of firearms as being “more than 2000.”  Several rumors regarding famous figures were also found within the information.


This kind of hearsay was an important information source, useful in providing excuses for the clan’s destruction, and Nakajima believes the shogunate used this type of information gathering capacity to threaten the various clans.


‘Hidden Racoon Dog’  and ‘Hidden Fox’


Furthermore, in “Ninja Tactics: Reading the Secret Manuals,” Nakajima introduces the “Eight Methods” for evading capture, taken from the Bansenshukai.


The eight methods are: (1) Racoon Dog Escape, (2) Firecracker Gun, (3) Hishimaki Escape, (4) Throwing stones Technique, (5) Becoming the Pursuer Technique, (6) Escapee, Open the Gates! Technique, (7) Escapee, Close the Gates! Technique, (8) Hidden Racoon Dog & Hidden Fox.



The unique techniques are those with animal names. The Hidden Racoon Dog involves escaping up into a tree, and Hidden Fox uses a Lotus leaf to hide one’s face when escaping underwater. Neither are particularly specialized techniques, but as Nakajima analyzes, “No one expects a Racoon Dog or a Fox to be hiding nearby. It involves a kind of mind game…. The ninja developed an effective form of psychological warfare, based on their keen observation and experience.”


(5) involves escaping by acting the part of the pursuer, (4) involves throwing stones in water to give the impression that you are making a water escape.


“In tense situations, such as those involving pursuit or attack, the capacity for decision making and distinguishing is reduced. That is what ninja target,” said Nakajima.


From the rich variety of techniques used, we can come to understand just how much ninja studied the human psyche.


On June 27, 2017, Japan's ninja associated cities Koka (or Koga), Shiga Prefecture and Iga, Mie Prefecture signed an accord for cooperation on tourism. The mayors and officials of both town had a first meeting with the traditional ninja costume on that day at Koka. 




(Click here and here to read the original report in Japanese.)




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