In 1955 Miyagi won the
U.S. National Championships men's doubles title at the
Longwood Cricket Club in
Boston with compatriot
Kosei Kamo after a five-set victory over Americans
Gerald Moss and
Bill Quillian.
Hurricane Diane roared through New England in August 1955, flooding the tennis courts and delaying the tournament for a week. When the tournament resumed many of the leading players such as
Ken Rosewall,
Tony Trabert,
Lew Hoad, and
Vic Seixas had already left which reduced the quality of the competitors remaining in the men's doubles draw. Miyagi won the Japanese tennis championships in 1954, 1955, 1957, and 1960. Between 1952 and 1963 he played 16 times for the Japanese
Davis Cup team. At the 1962
Asian Games in
Jakarta,
Indonesia he won a gold medal in the men's doubles competition with
Michio Fujii and a silver medal in the men's singles competition. ==Grand Slam finals==