In the later part of the Japanese occupation of Korea, many Koreans went to Japan to further their education and to learn martial arts. One of them was Choi Yong-I (who, due Japanese immigration laws, later changed his name to the Japanese name Masutatsu Oyama), who was born in July 27th, 1923 in a village in Southern Korea.
At the age of 9, while staying on his sister's farm in Manchuria, he began studying the southern Chinese Kempo form known as "eighteen hands." In 1938, at the age or 12, Oyama traveled to Japan with the desire to enter an aviation school and become a fighter pilot. In 1941, he entered Tokyo Takushoku University to study aviation but he put more of his energies into the study of karate. He continued practicing Judo and boxing, and his interest in martial arts led him to the dojo of Gishin Funakoshi and thus, he started practicing Okinawa karate.
With his dedication, Oyama progressed quickly and by the time he was 20 years old he had obtained his fourth Dan. It was at this time that Mas Oyama entered the Japanese Imperial Army and began studying Judo in the hope of mastering its holding and grappling techniques. When he stopped training in Judo, after about 4 years, he gained a fourth Dan. He also trained in Goju-ryu for two years under Neichu.
Following the defeat of Japan after the Second World War, Oyama like all other young Japanese, was thrown into a personal crisis. He found a way out of his despair by training with So Nei Chu, a Korean master of Goju-ryu karate. This great teacher, renowned for the power of his body and deep spiritual inclination, had a profound influence on young Mas Oyama. Master So taught him the inseparability of Budo and the spiritual fundamentals of Buddhism. After a few years of training, master So advised Oyama to make a firm commitment to dedicate his life to the martial way and retreat to a mountain hideout and train his mind and body.