By Pertti Ruha
The purpose of henka is to eliminate all traces of predetermined movements, to ride on the opponent’s form, to blend in with the orientation of the form and return to its source.
It moves into the opponent’s kūkan  and withdraws without leaving a trace, without thinking about the attack or defense, by following only the laws of nature, and without applying force one can follow and “ride” the opponent’s form and then break it.
Compare this with surfing the crest of a wave. This is called Ukiashi (floating foot; 浮足) – The foot that floats on water because it is like the floating feeling you experience when you have control of the opponent’s balance and intentions all the way to its innermost core.
Use your body and gravity to eliminate all forces that you can capture, using the correct movements to act according to the situation. An improvised version of kata  that fits the situation but is spontaneous and pops out of nowhere. This can be compared to the standard game opening moves found in Igo  and chess. Although we use the word ‘standard’, the content is unique. The “content” is henka, then the inside and outside (omote and ura; 表裏) are combined by a subtle feeling. We can then be free to focus on the forces of natural movements, which is the purpose of henka.
 Kūkan 空間 lit. “Empty Space”, here it refers to taking advantage of the special form of the opponent’s technique and skills.
 Kata 型 or 形 “form” or “model”, a sort of package for archiving and passing on knowledge. On may understand it to be a sort of teaching module.
 Igo囲碁 Commonly called “Go”, is a sort of Japanese and Chinese chess game, that unlike in western chess, is focused on multiple battles and controlling “space”.
Ruha, Pertti. Henka. (February 21st, 2013). translated and Edited by Luke Crocker (May 28th, 2015).