Yōkō Gushiken, Mar. 2003
Yoko Gushiken (具志堅 用高 Gushiken Yōkō, born June 26, 1955 in Ishigaki, Okinawa, Japan) is a Japanese former professional boxer from 1974-1981. The southpaw’s professional record is 23-1 (15 by KO) and he held the title of WBA Junior Flyweight champion 1976-1981. Following his retirement from boxing, he remains popular in Japan as a tarento having signed a contract with Ohta Productions. Gushiken is part of the 2015 class for the International Boxing Hall of Fame. (Source Wikipedia)
See related story by Yuri Kageyama, “Gushiken comes to terms with boxing legacy,” Japan Times, 2 July 2015.
liuchiuan 
I heard through the grape vine that most of the best boxers in Japan are Okinawan or were trained in Okinawa. I heard of Yoko Gushiken, even though I am not a boxing fan.
Howzit, Surfer. Interesting observation. Here’s a possible explanation by “Todd Mahoney who is the only foreigner to own a certified boxing gym in Japan recognized by the Japanese Boxing Federation. Mahoney divulged that all kinds of boxing champions have been born in Okinawa that I was unaware of, such as Shigeru Nakazato and Akinobu Hiranaka just to name a few. Mahoney went on to say that some of his junior high school disciples are going to the mainland and coming back winners every month, going from Prefecture to Prefecture and taking home gold medals. He reckons the reason Okinawa produces so many good boxers is because of the lack of distractions on Okinawa” (David Higgins, “Tough Guys in Okinawa City,” Japan Update, 9/28/13). The same seems to apply in Hawaii’s early AJA boxing history. See Joseph R. Svinth’s article.
I think Okinawans, in Okinawa, in general tend to accept foreign ideas and concepts into their culture more readily than the Yamantunchu. I guess when western/American-style boxing first came into mainland Japan, the Yamatunchu probably saw it as a foreign oddity, whereas the Okinawans on the other hand saw the merits of the sport and excelled at it.
Your theory probably explains a lot about why Uchinanchu have gotten into boxing. It’s historically sound, too, since they’ve had to learn how to adapt to the more powerful countries that surrounded their tiny islands. They picked up a lot from the Chinese and the Japanese early on, and after the war they quickly absorbed a lot of American culture from the occupation forces.