From Shiro Kuma's Weblog by kumafr
Why is the Ten Chi Jin Ryaku no Maki so important?.
Until 1990, we had very little knowledge about the schools and the weapons. Remember that we really began the weapons in 1993 with the bô and the study of the schools only in 1998! From the beginning of the Bujinkan (and more precisely when the Togakure Ryû Ninpô Taijutsu was published in 1983) the basics were transmittedthrough the Ten Chi Jin Ryaku no Maki. Each student at that time was studying the Ten Chi Jin Ryaku no Maki to improve his fundamentals. The Ten Chi Jin Ryaku no Maki was the basic program to reach the black belt. The spreading of the Bujinkan over the last twenty years has abandoned the Ten Chi Jin Ryaku no Maki and it has been often discarded by the new generation of teachers.
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What is a Bujinkan black belt?
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A Bujinkan black belt is someone who knows the Ten Chi Jin Ryaku no Maki so well that every technique demonstrated looks like a patchwork of elemental bricks taken from the Ten Chi Jin Ryaku no Maki. Too often students receive a black belt without the knowledge of the Ten Chi Jin Ryaku no Maki and this lack in their practice leads to big flaws in their movements. In 2009 I gave a 5-day seminar on the full Ten Chi Jin Ryaku no Maki in India. When the Indian group went to Daikomyô Sai last December they told their teachers that they could see every component of the techniques taught by sensei and the shihan and recognize the strength of the Ten Chi Jin Ryaku no Maki.
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Are you a Bujinkan black belt?
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Then you must know “by heart” the ten and the chi and be familiar enough with the jin. Without this basic knowledge you will not be able to go far within the Bujinkan system. The heart of “kokoro no budô” is the Ten Chi Jin Ryaku no Maki. Learn it, study it and you will see your technical level excel and reach a new understanding. Without studying the Ten Chi Jin Ryaku no Maki attending seminars is a loss of time. It is like watching a movie of which you are not part of. Learn the Ten Chi Jin Ryaku no Maki and become the actor your own life instead of being a passive observer!
Ryaku in Japanese means “principle” but also “truth”. Learn the truth of things and you will become a true human being able to link the sky and the earth; able to be one with nature. 
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