Higher knowledge of ninjutsu traditions and techniques was only imparted after the student had proven to be of tactical value as an agent. In this way, the most secret of shinobi traditions were protected through the implementation of a sort of portcullis to higher knowledge that required proofs of loyalty and promise as an agent prior to gaining full access to the deepest secrets of the art. So unless modern “ninjutsu” schools regulate access to deeper and more deadly historical traditions in the same manner, or based upon belt rank, the “ninjutsu” martial artist can expect that he/she will not learn the more sinister techniques of the ninja.
The students will not learn how to cook up explosives, how to infiltrate a residence, how to learn an attackers intentions, how to interrogate, torture, assassinate, or concoct credulous disguises. They will never be asked to survive in the wilderness, survey enemy territories, or kill another person over inadvertent exposure of a vital mission secret.
This is the reality – real ninjutsu that includes tactical training across various disciplines of warfare, does not exist as a “martial art”. As previously argued, the nominal forms of “ninjutsu” in modern society are at best diluted nuances of their progenitor (historical ninjutsu).
Adding to this argument, it is important to take note of what is written by the controversial “ninjutsu” martial arts authority Maasaki Hatsumi. As the 34th Grandmaster of the Togakure Ryu, he asserts that historical practitioners of ninjutsu were, “trained in eighteen fundamental areas of expertise, beginning with ‘psychic purity’ and progressing through a vast range of physical and mental skills.”
These skills moved beyond mere unarmed combat to include the aforementioned use of disguise, espionage tactics, explosives, and a myriad of proficiencies in the use of bladed, cord, chain, or projectile weapons. So far as one can tell, these 18 disciplines are not taught in full to Bujinkan members themselves.
If one were to assume that the credibility of Hatsumi as an authentic teacher of ninjutsu has been established, and that what he states is true, then the student of any school that offers connotations of “ninjutsu” should be aware of its inauthenticity on the basis of what is omitted from a manual-based curriculum.
What is more, the Koka Shinobi no Den Miraiki transcribed by Chikamatsu Shigenori contains incontrovertible evidence that the schools of modern day Koka “ninjutsu” (if not to include schools of the men of Iga as well) cannot possibly teach authentic/deep ninjutsu.
This incisive document consists of a verbatim dissertation on the art given by a Koka ninja master known as Kimura Okunosuke Yasutaka in the year of 1719 AD, and it supplies ten of his predictions concerning the demise of his shinobi traditions. Among the ten, he laments that the younger men of his century have no real interest in preserving the traditions of ninjutsu as the peaceful Edo period was affording the younger generations an easier life free of the difficulties of warfare.
Furthermore, he explains that the shinobi schools of his century were all headed by lesser ninja who never had access to the deeper secrets of ninjutsu nor any real experience in utilizing the art, stating that the traditions of ninjutsu were given in stages, and that candidates rarely attained the level of worth to receive the higher teachings. In fact, Kimura says that only one out of a thousand men would be found suitable to receive full knowledge of all the shinobi traditions whereas the rest would be taught shallow arts. Hence the reason Kimura perceived it to be inevitable that his art would fade with the passing centuries as the veteran ninja died out without a vessel to preserve their ways.
(Excerpt from Ninjutsu: A Commoner’s Guide)