It is not the yonkyo immobilisation that is presented here, but the fourth law illustrated by the yonkyo immobilisation, which is why O Sensei is careful not to write immobilisation: 之ョ第四法ト稱ス
For a long time, I passed on the knowledge that had been taught to me, but today I pass on what I learned directly from O Sensei, by listening to and respecting what he said.
‘Concentrate force in the fingertips of the left hand to project the opponent’s right hand upwards towards his shoulder’ - O Sensei (Budō)
A rule seems to emerge which is this: for the irimi principle to be manifested, all Aiki techniques must be executed by moving in four square steps. This is the meaning of the ideogram 方 in 四方 (shiho), and shiho nage is simply an application that illustrates this general rule particularly well.
"When the opponent's sword rises, you must clearly imagine within yourself the line (direction) that will guide the momentum of your attack – straight or diagonal, according to your choice." Morihei Ueshiba - Budō
O Sensei does not write sankyo (三教), nor does he write third pin as it has been translated into English. Instead, he writes 之ラ第三法ト稱ス: this is called the Third Law.
Tenchi, kokyu, kaiten, kaeshi, and shiho are technical principles present in every Aikido technique. Every Aikido technique must respect all of them in order for the unique principle of irimi in Aikido to be a reality.
