Sumitomo Bank was established as a private enterprise in November 1895 and reorganized as a limited company with 15 million yen of capital in March 1912.
[3] It opened overseas branches during the World War I era as the Sumitomo zaibatsu business became more international.
Sumitomo was the main bank for several major Japanese manufacturers during the early postwar era, including NEC and Panasonic (Matsushita).
[2] In the 1970s, it lost nearly $1 billion in the restructuring of Osaka-based general trading company Ataka & Co., which, combined with the contemporaneous bailout of Mazda, had a major impact on Sumitomo's finances, driving it down from the most profitable bank in Japan to being only ninth-ranked.
[2] In 1986, Sumitomo merged with Heiwa Sogo Bank in order to expand its presence in the Tokyo area.