Omi was born in Numata, Gunma Prefecture and graduated with a degree in Commerce from Hitotsubashi University. He joined the Ministry of International Trade and Industry and later served as consul general of Japan in New York City and as Director of the Small Business Administration. He resigned from the bureaucracy in 1982 to run for office, and was elected to the Diet of Japan in 1983.
Omi was appointed as Director of the Economic Planning Agency in 1997 and briefly as a state minister under Junichiro Koizumi in 2001. He was on a mission to the United States during the September 11, 2001 attacks.
Omi was Minister of Science and Technology 2001–2002. He was appointed Minister of Finance on September 26, 2006.
|Minister of Finance of Japan
- Japan's Abe Unexpectedly Names Omi Finance Minister, Bloomberg, September 26, 2006.
- Omi, Koji (22 December 2014). "Constructing a Global Science Forum". Science & Diplomacy 3 (4).
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