Who knows the joke that Japanese players wear steel plates every day?

Once in a competition, Americans took out a piece of cardboard and shouted it out. Then the Korean took out a board with a hole in it. The referee was very surprised. When he was about to announce the winner of the competition, he looked down and saw the Japanese. He took out a steel plate with a length of 3 cm h and penetrated it instantly. It took the referee a long time to say your name, and then he shouted, my name is "Nishikawa Okasaka"