In 1940 Kamikawa Yo graduated from the Law Department of Tokyo University.
After the graduation Yo Kamikawa entered the Research Department of the Foreign Affairs Ministry. He enlisted in the army (1942) and became 1st Lieutenant. After the war, served in various sections of the Ministry and assigned to the Overseas Office at Bonn, Germany (1952). Yo Kamikawa appointed chief of the Seventh Section of the European and American Bureau of the Ministry (1955).