The basic bunkai associated with various kata, however, is often overly simplistic. While this helps to learn the kata to a certain extent, the application itself in some cases becomes entirely unrealistic. As an example, the simplistic interpretation of an "uke" technique being a block leaves open a number of unrealistic situations whereby the kata is performed with a series of blocks, but no "uchi" or "tsuke" counter. Of course an adversary is not simply going to attack, have his attack blocked and then give up and find something else to do with his time.
With Oyo, we remain (for the most part) within the embusen (or shape) of the kata, but expand the application of the various techniques. An "uke" technique may therefore also be a form of "Uchi" to strike or counter-strike. We may also move away from the low basic stances and move to lighter more agile position as would be the case in an actual application. Within the study of Oyo, we also take into consideration the physiology of the human body. Some techniques may be subtly disguised as either joint-locks or even throws/projections, and the study of this physiology helps us to understand the such applications extrapolated from what appears to be a relatively simple technique.
Finally, as our understanding of the kata and its application progress, we move into the realms of more realism, whilst taking liberties with the form. We are no longer bound by the shape of the embusen for the particular kata. The techniques and application can therefore be performed in just about any direction. Here is where we start a true understanding of the kata, through the study of Henka.
Remember that the shape or form of a kata in no way represents the realistic position of the attackers, nor their timing or techniques of attack, and that the embusen in a kata is predominantly designed to maintain a common start and finish position for the kata. Indeed, many of the kata we practice, when viewed from above, are entirely symmetrical in their shape, with some techniques repeated to the left and to the right in near mirror image.
Similarly, in some dojos, some practitioners go "overboard" and attempt to ensure that every single movement of a kata must have a corresponding bunkai, and they often use this in a demonstration. Again, however, where techniques are repeated, this interpretation can lead to an unrealistic application. It is not necessary to demonstrate the entire kata with its existing shape (embusen) along with a flowing application. Think of the myriad of different applications for each technique.
Additionally, there may be "overlapping" applications between adjacent techniques, so it would be equally unrealistic to attempt to fit two different applications into the movements at the same time, where for example the last two movements of one application are the second and third of another application which continues with another couple of movements afterwards (I hope that makes sense?).
I encourage readers to use their imagination when working on applications, especially with Oyo and Henka. There are usually several different possible applications for a given set of movements, so it is a good idea to experiment with them.
Here are a few tips when working with Oyo and Henka which I have found useful over the years.
1. The application does not necessarily match the embusen of the kata. Try the application in different directions, or sets of directions.
2. A turn or pivot of the body does not necessarily mean that you are turning to face a new opponent… it may be a continuation of the application with the existing opponent in the form of a technique to the rear (ushiro-waza) or even a throw or projection.
3. Many open-handed techniques are applied to vital points. There is no point in executing a haito-uchi to the the side of the skull. In the real world, this could result in breaking the joints where the index and thumb intersect into the hand. Applying such a technique to a nerve ending, on the other hand, can be very effective.
4. Not all "Uke" techniques are blocks.
5. Often at the end of a kata, there are two "uke" techniques to finish the kata, such as in Empi or Meikyo where you complete with a shuto-uke in kokutsu-dachi, step back again with another shuto-uke in kokutsu-dachi. The second "uke" could simply be a mark of zanshin (awareness).
6. Never settle for only one application - there are numerous, so experiment and think outside of the box.
Over time you will find that experimentation with the Oyo and Henka associated with the kata applications will give your kata performance more "life and spirit", enhancing the overall performance both visually as well as mentally.