Mr. Ohshima left Japan in 1955 to continue his studies at the University of Southern California in Los Angeles. In January 1956 Ohshima Sensei led his first U.S. practice and in 1957 established the first university karate club at the California Institute of Technology in Pasadena, CA. In 1959 Ohshima Sensei founded the Southern California Karate Association (SCKA). This organization grew to become a nationwide organization, Shotokan Karate of America (SKA). In addition to being the Shihan (Chief Instructor) of SKA, Ohshima Sensei was recognized as Shihan of many other national organizations; thus his influence on karate is felt globally.
In August 2018 at the age of 88, Ohshima Sensei retired as Shihan. At his retirement, Ohshima Sensei appointed a Shihan for SKA and each international organization. Ohshima Sensei’s branch of Shotokan has become known as Shotokan Ohshima Dojo.