Koizumi was born in
Higashi-Kaseda,
Kagoshima Prefecture (now part of
Minami-Satsuma); his family were fishermen. He attended high school at night while working in a department store, and then attended law classes at
Nihon University while working as a secretary to a
Diet member. He graduated in 1930 and joined the
Rikken Minseitō political party. He was elected to the Diet in 1937. He married Yoshie Koizumi, the daughter of Rikken Minseitō director and postal minister
Matajirō Koizumi, taking her family name. Junya and Yoshie Koizumi had six children, including
Jun'ichirō Koizumi, who later became the
Prime Minister of Japan. Koizumi was purged from politics by the Allied occupation government in the late 1940s, but returned to the Diet in 1952. He was a close ally of
Nobusuke Kishi in the postwar years, served as Vice-Minister of Justice under
Ichirō Hatoyama and became
Director General of the Japan Defense Agency under
Hayato Ikeda and
Eisaku Satō. == See also ==