The man known as Gogen Yamaguchi (one of ten children) was born on January 20, 1909 in the city of Kagoshima, which is located on the southern end of Kyushu Japan. He was named Yoshimi Yamaguchi by his father, Tokutaro, who was a merchant, a school teacher and superintendent. His mother, Yoshimatsu, was Tokutaro's assistant. As a boy Yamaguchi trained in the art of Jigen-ryu Kenjutsu (kendo). As a young teen, when his family moved to Kyoto, Yamaguchi began studying Goju-ryu in the Maruta Dojo in Miyazai, Kyushu under Takeo Maruta, a carpenter by trade. Kendo training and his studies with Maruta gave Yamaguchi strong roots in the martial arts.

Later in life he picked up the nickname "The Cat". There are several theories on where the name came from. One is due to his long flowing hair resembling a lion's mane. Then there are those who say it is due to his preference for the cat stance in Goju along with his cat-like gaze he would often lock his opponents with. Another theory attributes the name to his post-war years teaching Allied troops karate in Japan. He would constantly walk up behind students soundlessly and displayed the grace and lithe movements of a cat when practicing Goju-ryu. Others say the name came from his legendary battle with a tiger. No one knows for sure, it could be any one of these; all of them combined or it could be none. Yamaguchi simply was "The Cat".

In 1929 Yamaguchi entered Ritsumeikan University in Kyoto and majored in Law. In 1930 he started the first karate club on the Ritsumeikan campus. It was not long before the hard training and distinctive breathing exercises (ibuki) made the club well know throughout the city. It was during this time that Yamaguchi began work on jiyu kumite, which translates as free fighting or sparring. Masters and teachers of this time stressed kata and were not very big on free sparring as techniques were done full force without control. The system Yamaguchi developed was based on the sparring system of kendo where points are scored for striking specific targets, and eventually would become the basis for modern day tournament fighting.

In 1931 Yamaguchi, age 22, was introduced to Chojun Miyagi, the founder of Goju. Up to this point in his training Yamaguchi had focused on the "hard" aspect of Goju. Yamaguchi was so well trained in the hard side of Goju that Miyagi gave him the name "Gogen" meaning "rough". After meeting Miyagi he became aware of his need to train his "soft" spiritual side as well. This is also when Yamaguchi was appointed as Miyagi's successor for Goju in Japan. According to Yamaguchi, Miyagi said, "Mister Yamaguchi, you are well qualified to be the successor of Goju school karate. I have nothing more to teach you." During a prior visit to China, Miyagi had taken what he learned there and modified some of Goju. Yamaguchi did not agree with these changes, believing the old ways were the best. When Miyagi left Japan to go back to Okinawa Yamaguchi began to do his own thing. This was the start of Goju-kai.