Mamoru Shigemitsu signed the Instrument of Surrender as Japan’s civilian representative.
Shigemitsu was Japan’s foreign minister in August 1945 and attended the ceremony as a civilian plenipotentiary. He signed first for Japan aboard USS Missouri, using the formula “By Command and in behalf of the Emperor of Japan and the Japanese Government.”
General Yoshijirō Umezu signed immediately afterward for Japan’s Imperial General Headquarters. The two men represented the civilian government and the military command structure, respectively.
Shigemitsu later returned to public service in postwar Japan, including another period as foreign minister. He was also tried by the International Military Tribunal for the Far East and convicted of war crimes, receiving a prison sentence before being paroled.