My area of expertise is in Kushida Sensei’s toshu and buki waza. It is a unique and beautiful art form that pays dividends in the practice of any martial art or movement system. If you are interested in koryu, I would look to Ellis Amdur and Meik and Diane Skoss plus others who are deeply committed to the study of various koryu.
Kushida Sensei’s Aikibuki system is based on the following koryu:
Tachi: Kashima Shinto Ryu and Katori Shinto Ryu. These were used in the times when people wore various coverings to protect themselves. The movements reflect the constraint of the protective clothing with stopping between the movements in order to study balance and precision.
The use of circles with cardinal lines and chords are the same you that you would see in the schools teaching sword in medieval Europe. A classic example being the Spanish Circle also known as La Destreza.
There were also kenjutsu schools in the same time period such as Kusumi Shinto Ryu that have similar kata. However, Kushida Sensei’s Aikbuki system does not reflect the style of later schools, such as Yagyu Shinkage.
Why is this relevant to Yoshinkan Aikido? If you look at a listing of people who studied Kashima Shinto Ryu you’ll see Ueshiba Morihei’s name. His Aikido of that time was very much like Yoshinkan Aikido.
Jo: Most of the Jo kata are based on Shindo Muso Ryu JoJutsu. One time, Kushida Sensei mentioned a spear koryu called Hozoin-ryu. But that doesn’t quite fit as Hozoin ryu has a crescent on the shaft to trip your opponents. Owari Kan Ryu Yari seems to be a better example.
Tanto: Kushia Sensei’s tanto kata are a mix of various tanto jutsu and Katori Shinto ryu wakizashi (short sword).
You’ll find plenty of examples of the koryu mentioned above on YouTube. I would recommend the website by Meik and Diane Skoss as an excellent resource to better understand the various Koryu. And Ellis Amdur’s Kogenbudo website as well as his various books are well worth your time.
Kushida Sensei’s kata, Kumi or Tandoku, can be used as a precise overlay of Yoshinkan Aikido technique.
The study of bukiwaza may not be for you, but I’m convinced, after studying them for 45 years, they add depth and precision to your Aikido and to your martial thinking.