Fuji Okamoto graduated from Toyo University of Commerce. He joined the Nippon Kento Club (Nikko) and became unofficial flyweight champion in 1924. Two years later, he won the first flyweight title at the All-Japan Amateur Boxing Championships on the grounds of the Yasukuni Shrine. At the 1928 Amsterdam Olympics he lost his first bout by decision against Irishman Frank Traynor. After retiring, he worked for Nikko, coaching amongst others the Japanese pro-champion Tsuneo “Piston” Horiguchi. Later, Okamoto established his own gym, the Fuji Boxing Hall. From 1957-62 he served as president of the Japan Professional Boxing Association.