Sonzai no Genkaku ryuu - "illusion of existence" style of kenjutsu - was passed down over 12 generations of the Himitsu family (Kaida makes the 13th), over about 250 years. Founded by Himitsu Ichiro, who had been blinded by a fever in his childhood, it requires not only great physical endurance and strength, but inherent aptitude for a little-known technique known as tamashii no shiryoku, or "soul’s sight," which runs in the Himitsu family. Ichiro perfected the technique and passed it on to his son. When the clans formed, the Himitsu family was chosen by the Minoru family to protect and guard them, and until the end of the Seiva wars in the year 302, the Himitsu descendents fulfilled their duty exceptionally.

Training in Sonzai no Genkaku ryuu is traditionally given to the eldest son of the family, by the father. Basic kenjutsu training begins at a very young age - often as young as five or six - but the true techniques are customarily withheld until the boy is fifteen years of age. In times of war, however, it is not uncommon for a student to begin the more secret stages of training at ten or eleven, provided the child is judged to have suitable focus and intelligence. The physical training requires great stamina and speed, and the mental training requires immense fortitude and powers of concentration.

The first stages of physical training are still basic kenjutsu, except they are done blindfolded to help decrease the student's dependency on his vision. The student must learn how to move without using his eyes for guidance; that is, he must know the range of his body and sword, be able to perform basic kata with his eyes closed and not deviate from the prescribed footing and positioning, and so on. Once his master has deemed him ready to move on, the student is trained in meditative techniques to engage his mind and in grueling physical training to develop the strength and stamina needed to learn the complex swordsmanship.

Sonzai no Genkaku kenjutsu style focuses on speed, form, and strategy, with the premise of its success being that the student is faster, trickier, and more accurate than his opponent. Many of its kata, or forms, involve feints followed by swift, one-cut attacks, and the student is expected to be able to manipulate his opponent's expectations in order to draw him into vulnerable positions. Some of the more advanced attacks also require the one-handed use of a katana in order to take advantage of reach and whatever openings the opponent may unwittingly provide.

The physical aspects of the technique alone are strongly offensive because most of the kata are designed to kill in a single strike without giving the opponent a chance to dodge. Without the addition of tamashii no shiryoku, the student's defense is weak and easily penetrable. It is the soul's sight that allows the student to read his opponent and give him the time needed to defend.

Tamashii no shiryoku is unlike true eyesight - that is, a person using even the most elevated form of the technique is not aware of appearances as perceived by the eye. He cannot describe what he "sees" when he fights using the technique, because he does not "see" anything. Instead, tamashii no shiryoku allows the user to sense the energy of his opponent's muscles and changes in his opponent's mental state. Where true sight can be deceived by a feigned attack or by an optical illusion, a well-trained user of tamashii no shiryoku cannot fall prey to such artifice. Instead of reacting to visual cues, the user's mind reacts to the hidden movements that define each motion. By knowing what invisible motions make a feigned attack different from a real one, the user can tell whether to block or to use the time for a swift attack or other maneuver. By similar principles, the user can detect where his enemy will move or attack before any visible change of position is made, thus allowing him to react much more quickly. The technique is almost always used while one's eyes are closed, since if it is used while the eyes are open, the two senses can "overlap" - simultaneous triggers from both senses (especially during feigned movements, where each sense perceives a different action) can cause intense confusion, dizziness, a feeling of having impaired or double vision, and at times can cause the user to pass out.

There are three "forms" of tamashii no shiryoku, and a student's proficiency in the use of the technique is partially indicated by which forms he is able to use. The first form, henji ("response"), is considered the most basic. This is the form that allows a user to sense his opponent's motions, and is often used as a test to tell whether or not a student is able to grasp the technique. A student who has mastered henji can defeat an enemy with his eyes closed that would be slightly above his level under normal conditions. He can judge his opponent's actions, and sense how his opponent will move, with much greater speed and accuracy than he could using his eyes, and thus can react more quickly. This form requires substantial concentration and can rarely be maintained for over an hour. The sensation felt upon activating henji is often described as attempting to stretch a handful of rubber bands (though the effort is, of course, exerted solely by the mind), and maintaining it is, as one would expect, rather like holding said rubber bands in their stretched-out position. Ending the technique feels much like releasing those rubber bands – there is a moment of recoil that, depending on the student, may be anywhere from one to six seconds. Often the recoil manifests itself in blurred vision and a moment of extreme muscle fatigue (sometimes even total loss of muscle control) while the body and mind recover. Naturally, a degree of lasting fatigue is to be expected.

The second form, shuui ("surroundings"), requires the student to have significantly reduced his dependence on vision and allows him to sense hostile actions which are in extremely close proximity, as well as changes in emotions of those around him. A student who has mastered shuui can invoke it with minimal concentration, maintain it with little to no effort, and sustain it for very long periods of time without conscious attention to it. He is aware of powerful onsets of surprise, fear, anger, pain, and happiness in those around him. He can sense imminent attacks, and is thus able to defend himself against ambushes, assassinations, and attacks from behind. He is able to use the form with his eyes open. This form requires a great deal of time and effort to master, but once properly learned, it is very easy to use. It cannot, however, be used at the same time as henji.

The third and final form, kanzen ("completion"), has only been attained by two members of the Himitsu family line, these being the founder of Sonzai no Genkaku ryuu and Himitsu Tomoshige, the eldest son of the twelfth generation. This form combines henji and shuui into a superior, heightened awareness. As well as the abilities granted by the first two forms, a student who has mastered kanzen can predict his opponent's movements with more speed and accuracy than when using henji, and can detect the emotions of others much more sensitively. He can accurately aim long-range projectile weapons without the use of his eyes. He can sense the location of inanimate objects and is able to work around them when fighting. It is not possible to read an opponent's mind using kanzen, but the illusion of such a talent is often created by a very skilled user (Tomoshige was often asked about mind-reading; he was said to have never confirmed or denied it). This form may require a lifetime of training, practice, and study before it can be attained, and even then, only those with exceptional aptitude may hope to master it. Himitsu Ichiro was said to have been able to maintain it for twelve hours at a time; Himitsu Tomoshige once sustained it for a full day on the battlefield, though he was severely affected by exhaustion afterwards. Because the length of time required for study is often longer than a student's master will survive, the student is expected to attempt achieving kanzen without guidance.

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