Kasahara was born on March 26, 1918. He played for Keio University. He won the 1937 Emperor's Cup. He also played for Keio BRB which was consisted of his alma mater Keio University players and graduates. He won the 1939 and 1940 Emperor's Cup at the club with Yukio Tsuda, Hirokazu Ninomiya and Saburo Shinosaki. 1940 Emperor's Cup was the last Emperor's Cup before the war because Emperor's Cup was suspended for World War II from 1941 to 1945.