In 1941, Kawamoto served in the military for World War II and was detained in the Soviet Union following the war for 4 years (Japanese prisoners of war in the Soviet Union). In December 1949, when he was 35 years old, he returned to Japan and came back as player at Osaka SC. Osaka SC won the 2nd place at Emperor's Cup 3 times (1951, 1952 and 1953).