This kata was created by Shimabuku himself, based upon the Kusanku kata he had
learned from Kyan. The following information was gleaned from a personal
communication from A. J. Advincula (1998), who studied with Shimabuku in
Okinawa. Before studying with Taira Shinken in the late 1950s and early 1960s,
Shimabuku only knew the cudgel tradition of Tokumine that he had learned under
Kyan, as well as a sai kata called Kyan no Sai. It is unknown whether this sai
kata was created by Kyan or created by Shimabuku from techniques that he learned
Kusanku was, along with Chinto and Passai, Kyan's specialty, and this may have
influenced Shimabuku's decision to create a sai kata from this form.
According to Advincula (1998), Shimabuku originally included kicks in the kata,
but later removed them. Upon being asked why, Shimabuku stated that when he
first created Kusanku Sai, he knew little about kobudo, but after gaining more
experience apparently removed the kicks.
Kobudo of Shimabuku Tatsuo by Joe Swift, 1998