Seisan (or Seishan)
Season was a Chinese envoy who taught the kata in Naha Okinawa. While it was likely he was not the creator of the kata, it was named after him. The kata became popular in Naha.
Shinun ‘Peichin’ Takahara (1683-1762)
It is uncertain if Takahara learnt the kata from Seisan or from someone who trained with him. Takahara, a martial arts master and astronomer, modified the kata in name and appearance, combining his love of martial arts and astronomy. The kata continued unchanged in Naha and would be passed down through Goju lineage as Seisan.
‘Satunushi’ ‘Tode’ Sakugawa (1733-1815)
Student of Takahara and Okinawan teacher of Soken Matsumura.
Sokon “Bushi” Matsumura (1796-1893)
Student of Sakugawa and teacher of Itosu.
Yatsutsune “Ankoh” Itosu (1830-1915)
A student of Sokon Matsumura’s, taught the kata to his student – Gichen Funakoshi.
Gichen Funakoshi (1868-1957)
Founded Shotokan karate and incorporated Hangetsu into his system. This was one of the few kata whose name he did not change. This was because the name had already been changed from its original Chinese name.
While many styles incorporate Hangetsu, GKR derives this kata from Shotokan karate.