In December 1895, at the recommendation of director Nakamigawa Hirojirō, Ikeda began working at Mitsui Bank. After being assigned to the Osaka branch, he was made director of the bank's Ashikaga branch, following which he worked on reform proposals for the underwriting of municipal bonds for Osaka, and for deposit agreements between banks. He was then sent back to the United States in 1898 to study banking modernization. After his return in 1900, he rose rapidly through the hierarchy within the Mitsui zaibatsu. In 1904, he married the eldest daughter of managing director Nakamigawa Hirojirō. He helped establish Mitsui Bank as a stock company in 1911, of which he became a director and was appointed managing director in 1919.
