When you look at the meaning in a dictionary you get many answers as usual in Japanese. But I found two definitions that serve or purpose today.
The more logical one is 士官 officer, but another definition is 弛緩which means relaxation! In the army officers are not known for being “relaxed” but then when you learn how to use Shikan Ken properly, the antinomy between these definitions vanish and begin to make sense. I will demonstrate it later.
Historically Shikan Ken was used to protect the tips of the fingers in a fight involving 鎧 Yoroi (armor) and swords . As you know the hand protection on the Yoroi is leaving the last two phalanxes unprotected. By folding the fingers, they get protected by the metallic plate covering the back of the hand.
Many other types of “Ken ” can be used in a fight such as: fudô Ken, happa Ken, koppô Ken, shutô Ken, boshi Ken. How?
不動 fudô Ken (immobility) is used for direct hit but the resistance of the Yoroi makes it problematic to be efficient, except maybe to get uke’s balance. The fingers are also well protected.
葉っぱ happa Ken (leaf) can be used for pushing or slapping the opponent. It might create an opening which is entered then with another hiken jû roppô* weapon. The fingers are not protected here.
骨法 koppô Ken (the knack) is very limited in use even though the hand protection is composed of several plates, the hit power is limited by the protection (no sharp angle possible). With the hand protection you cannot really use the extension of the knuckle. The fingers are protected.
手刀 shutô Ken (the hand as a sword) has limited use against an opponent wearing a Yoroi, but it can come after a Shikan Ken in the development of the action. The thumb then support the plate protecting the hand and the hit is done not with the flesh but with the metallic plate. This is why in shutô, the thumb is on top of the second phalanx of the forefinger.
拇指 boshi Ken (thumb or big toe) is also usable but on soft spots only. The thumb can be supported by the plates. This is why sensei taught us three different thumb positioning when we entered the realm of Yoroi jutsu.
So as you understand it now Shikan Ken is the best suited Ken to be used in a Yoroi fight. But it also wroks fine in regular unprotected taijutsu.
But if this Ken is so efficient why is it that each time we try to use it, we end up with pain in the fingers joints when we hit the target?
I did my best not to think about the predictable and painful outcome of it, but with no success. And like many of you I began to discard Shikan Ken, using it only for cultural purposes (repeating the hiken jû roppô). It was like that until I decided to ask directly Hatsumi sensei how to do it correctly… On this planet if there is someone knowing this it must be sensei. And he answered.
But before I give you Sensei’s answer, I find it amazing the general behavior of many Bujinkan visitors to Japan when it comes to learning.
When you go to Japan to meet your teacher, ask everything you need to know because once you are gone no one will give the answer you need. You train for your own good. Sometimes Sensei will answer you and these are the best answers as they are coming directly from the source, they are not tampered by any filter. He might also not give you any answer and this is OK too, at least you tried. If you don’t try to learn by yourself, he will not do it for you.
So one day in class I went to him and asked: “sensei why is it that each time I use Shikan Ken, I nearly break my fingers? “
His answer was so simple that I felt stupid. Here it is.
When you hit your opponent with Shikan Ken, your Ken starts from a relaxed fudô Ken (the second definition: relaxation), then on impact you have to overextend the knuckles and the hand at some angle, and tense all the fingers in the process. If you try this in your next class you will see that there is no more pain.
The basics are called basics because they are the foundation on which you build a strong taijutsu. And to know your basics, you have to research endlessly and ask a qualified person. And the most qualified person in the Bujinkan, is our Sôke, Hatsumi sensei.