Made a captain in 1936, Komura participated in the attack on Pearl Harbor and the Battle of Midway as the captain of the seaplane heavy cruiser Chikuma. In June 1942, he took command of the new battleship Musashi. Promoted to rear admiral and appointed chief of staff of Third Fleet in December 1943, Komura assisted Vice Admiral Ozawa Jisaburo in the Battle of the Philippine Sea in June 1944 and the Battle of Leyte Gulf in October. In the latter engagement, Ozawa and Komura drew Admiral William Halsey's U.S. Third Fleet away from Leyte and completed their mission as a decoy, although at considerable cost in Japanese ship losses.
On 5 April 1945, Admiral Toyoda Soemu ordered Operation ten-ichi (heaven number one) in which the Second Fleet, consisting of the flagship Yamato, the cruiser Yahagi, and eight destroyers, would steam to Okinawa in an attempt to destroy U.S. support ships off the landing sites. The ships only had fuel sufficient for a one-way voyage, for the plan called for Yamato to inflict as much damage as possible and then be beached as a stationary battery. The operation was a suicide mission, but Komura joined it aboard the Yahagi. In the East China Sea on the early morning of 7 April, the Yahagi was attacked and sunk by planes of U.S. Vice Admiral Marc A. Mitscher's fast carrier Task Force 58, but Komura survived. The Yamato was also sunk the same day. That evening, Admiral Toyoda ordered the remaining destroyers of the task force to return to Japan. In May 1945, Komura was appointed commander of the Yokosuka Naval Station.
Three years later, he was hired by the U.S. occupation forces at Yokosuka to manage 27 patrol vessels at the naval station. He also helped establish the Japanese Naval Self-Defense Force on the outbreak of the Korean War in 1950. He did not join that force but worked with the U.S. Navy for 11 years. Komura died in Tokyo on 7 February 1974.
Morison, Samuel E. History of United States Naval Operations in World War II. Vols. 2, 4, 5, 9, 10, and 11. Boston: Little, Brown, 1947–1952.; Yoshida Mitsuru. Requiem for the Battleship "Yamato." Trans. Richard Minear. Seattle: University of Washington Press, 1985.