Short answers, pulled from the story.
Mamoru Shigemitsu was a Japanese diplomat and politician who served as Minister of Foreign Affairs three times. He is best known for signing the Japanese Instrument of Surrender as the civilian plenipotentiary of the Japanese government on the 2nd of September 1945, aboard a battleship alongside General Yoshijiro Umezu.
Shigemitsu lost his right leg on the 29th of April 1932, when Korean independence activist Yoon Bong-Gil threw a bomb at a reviewing stand during Emperor Hirohito's birthday celebration in Shanghai. Shigemitsu walked with an artificial leg and a cane for the rest of his life.
Yes. Despite his well-documented opposition to Japanese militarism, the International Military Tribunal for the Far East convicted Shigemitsu of waging aggressive war and failing to do enough to protect prisoners-of-war from inhumane treatment. The tribunal sentenced him to seven years in prison, the lightest sentence handed down to anyone convicted at the trial, citing his regular opposition to militarism. He was paroled in 1950.
After his parole in 1950, Shigemitsu was elected to the Lower House of the Diet of Japan in October 1952 and became Deputy Prime Minister under Prime Minister Ichiro Hatoyama in 1954. He also served as Foreign Minister from 1954 to 1956, represented Japan at the Bandung Conference in 1955, and helped negotiate the Soviet-Japanese Joint Declaration of 1956.
The Bandung Conference was an international gathering held in Indonesia in April 1955. Shigemitsu represented Japan at the conference, which marked the first time Japan had participated in an international conference since the League of Nations.
Japan became the 80th member of the United Nations on the 18th of December 1956. Shigemitsu addressed the United Nations General Assembly that year, pledging Japan's support for the founding principles of the organization and formally submitting Japan's application for membership.