Tomiichi Murayama
Kubo started his career as a high-school teacher. Then he involved in politics, and in 1963, he was elected to the Kagoshima Prefectural Assembly where he served for three terms. He was first elected to the upper house in July 1974 from Kagoshima. Until 1993 he served as chairman and a member of different committees at the house, including the budget and finance committee in the upper house. In September 1993, he was named as secretary general of the Social Democratic Party during the term of the party chief Tomiichi Murayama. He was also chief finance policy strategist and deputy chairman of the party.