What is "seisan"

The karate kata Seisan (alternate names: Sesan, Seishan, Jusan, Hangetsu) literally means '13'. Some people refer to the kata as '13 Hands', '13 Fists', '13 Techniques', '13 Steps' or even '13 killing positions', however, these names have no historical basis.

Seisan is thought to be one of the oldest kata, being quite spread among other Nahate schools. Shito-ryu has its own version and different versions are now practised even in Shurite derivatives like Shotokan (called Hangetsu) and in Wado-ryu (called Seishan). Isshin-ryū also adopted this kata. This kata is also practiced in Korean styles such as Tang Soo Do and Soo Bahk Do and is called Sei-Shan or Seishan in Korean. Due to its difficulty, this kata is often reserved for advanced students.