A karateka who spend 2 years on hian katas and then 3 months on kankudai has more ability and understanding than a student who spent 2 years and 3 months on kankudai alone .

Can you explain why you believe that to be true?

To play devils advocate:

When Gichin Funakoshi compiled his original 15 kata syllabus it formed a complete system of karate education in self defense. This is one of the first attempts at a kata syllabus that goes beyond 3-5 forms and so it was designed to be studied differently.

Funakoshi pioneered a method of kata study whereby you learn the forms in sequence and technique only, before returning to the start in order to study and develop martial skill through application study.

Funakoshi changed the content of some forms to minimise overlap with other forms as there were more than usual, but also to minimise over-specialisation. More forms mean less time for niggling details. In understanding that variations of individual techniques are the fruit of application study, and that details like a wrist position in a form is not training that benefits the student physically. Standardised movements, easier to teach and learn and more athletic in nature were given as replacement for the more intricate techniques.

As he developed this method further the order of the kata changed. He went from the old deep study method of learning core kata deeply before doing the same to peripheral forms (that had kanku dai as the 3rd form) to a sequence that takes coordination difficulty as paramount. This is what we have today, with Pinan shodan and nidan reversed and kanku dai way down the list.

All this modification towards a larger syllabus produced a set of kata that built directly upon one another, the gaps in the early forms being filled in by later ones and vice versa. Shotokan's kata though retaining the material for deep study are no longer designed to be taken alone.

To give examples of this is difficult though because we have so little idea of what the kata looked like originally. Funakoshi's lineage is through Matsumura over Itosu so Shorin ryu is not a strong enough comparison. Furthermore due to the development of the ryu, all of which use large syllabus's, they're kata have all been through varying degrees of the same process. Matsumura Seito Shorin ryu is the clearest example of the difference between kanku dai with standardised techniques and old style detailed in depth kata.

Here's one to look at.

By my assessment, at least some of the technique that is missing from Kanku dai can be found in hiean sandan.

So in summary, failing to study the hiean kata prior to kanku dai means that you are missing a portion of the full application potential of the kanku dai system.

Kusanku Dai or Kushanku Dai is a kata I still need to put more practice into. The critical jump always has my legs waving in the air.

This kata has many movements that are exactly like the movements in many of the pinan katas. Correct me if I am wrong this is due to the fact that the pinan katas were made around more complex katas to give it to the masses in a more digest able form.

Overall I enjoy the quick movements that this kata has to offer.

but,these are just my thoughts as an orange belt,shito ryu practitioner.

-Nijil