Sosui Ichikawa (市川 素水; August 29, 1924 - March 7, 2005), was a Japanese martial artist born in Ueno, Tokyo, Japan who was the 4th Sōke of the Zen Nihon Goju-Ryu Karate-do Renmei (全日本剛柔流空手道連盟) and founder of the Sosuikan (素水館).

Two Okinawan men in his unit were also students of Karate-do, when they were not engaged in naval duties during their time at sea together, he was able to learn karate from them while aboard a battleship.

Japan's postwar situation was difficult due to the devastation that the country suffered during the war; since behind the Ichikawa residence rests an Inari shrine that hosted many festivals, Sosui was often called upon to deal with troublemakers and break up fights in the area.

Izumikawa was a top student of Sekō (Seiko) Higa (比嘉 世幸) who trained directly with Naha-te master Kanryō Higashionna (東恩納 寛量) and the founder of Goju-Ryu Karate-do Chōjun Miyagi (宮城 長順).

Ichikawa grew the number of students within a brief time when he first began teaching; therefore, classes had to be, temporarily, taught in a nearby park.

Sosui Ichikawa would teach the Goju-Ryu he learned from Izumikawa at the Sosuikan (素水館) dojo while still doing his own research and development.

Ichikawa would ultimately come to write his text, the Kōshu-do (交手道),[4] which was only handed to the most senior students, and it represented the culmination of his lifetime of study.

[6] The Okinawan Karate-Do Renmei accepted Sosui Ichikawa as Hanshi (範士), Jūdan (十段) in 1983, with Yuchoku Higa (比嘉 佑直) issuing the certificate.

Ichikawa Sensei also studied and practiced other styles, including Daitō-ryū Jujutsu (大東流 柔術) and Jūdō (柔道), and held dan ranks in both.

[7][8] As a result of his research, he expanded beyond the Sekō Higa (比嘉 世幸) lineage of Goju-Ryu and created many of his unique techniques and concepts.

Kenjiro Chiba (千葉 拳二郎), Masashi Sudo (須藤 雅史), Fusaaki Hattori (服部 房明), Masaaki Sakai (酒井正明), Tadahiko Ohtsuka (大塚 忠彦), Kiyoshi Yonemoto (米元 清), Kazunobu Tsubamoto (鍔本 和伸), Shojiro Jibiki (地引 昌次郎), Tadashi Yokoyama (横山 忠衛) and Robert Taiani were among his students.