He joined the Mitsusbishi Corporation that same year and continued with them his entire career. Kojima held various positions in the corporation in Tokyo, in Saudi Arabia and the United States.[3][4] In 1995 he was appointed to Mitsubishi's Board of Directors as an inside director (取締役).[2] In 2001, he went from being managing director of the corporation's merchant banking group to vice president; and in 2004 he moved up to president and CEO, when then president Mikio Sasaki replaced the out-going Minoru Makihara as chairman of the board.[5] In 2010, Kojima himself left the position of president and CEO to become chairman of the board of directors.[6]