Meaning 13, some people refer to it as 13 hands, 13 fists, or 13 steps.
Customarily taught in both Shuri and Naha, this kata, following the
tradition of Kyan Chotoku, is the first kata the Isshinryu student learns.
It is unclear exactly what the number 13 actually represents. Some think
it was the number of techniques in the original kata; some think it
represents 13 different types of "power" or "energy" found in the kata;
some think it represents the number of different application principles;
some think it represents defending against 13 specific attacks; and some
think that it is the number if imaginary opponents one faces while
performing the kata. Out of all these theories, this author must disagree
with the last, as it is highly unrealistic that kata teaches one to handle
such situations. On the contrary, kata was designed to teach the
principles needed to survive more common self-defense situations, rather
than a long, drawn out battle against several opponents (Iwai, 1992).
Kinjo Akio, noted Okinawan karate researcher and teacher who has traveled
to China, Hong Kong and Taiwan well over 100 times for training and
researching the roots of Okinawan martial arts, maintains that this kata
originally had 13 techniques, but due to a long process of evolution, more
techniques were added to it (Kinjo, 1999). He also maintains that the
Okinawan Seisan kata derives from Yong Chun White Crane boxing from Fujian
Province in Southern China.
It is unsure who brought this kata to Okinawa, but we do know that in
1867, Aragaki Seisho (1840-1920), a master of the Chinese-based fighting
traditions (Toudi) demonstrated this kata (among others) in front of the
last Sappushi, Zhao Xin (Tomoyori, 1992; McCarthy, 1995, 1999).
The main lineages that include Seisan include those passed down from
Matsumura Sokon, Kyan Chotoku, Aragaki Seisho, Higaonna Kanryo, Uechi
Kanbun, and Nakaima Norisato, among others. Shimabuku learned this kata
from Kyan. Both the Kyan and the Shimabuku versions of this kata strongly
resemble the Matsumura no Seisan (see Sakagami, 1978).
The "Master Seishan" theory, which claims that the kata was brought from
China to Okinawa by a Chinese martial artist named Seishan (or Seisan) is
uncorroborated myth at best, probably propagated by well-meaning, but
not-so-well-researched American Isshinryu instructors. This legend cannot
be found in any of the literature coming out of Okinawa or Japan.
The Kata of Okinawa Isshinryu Karate-do: An Informal Discussion on their
Possible Origins by Joe Swift