From Sega Retro
Hisao Oguchi joined Sega in 1984. In 1993, he became the Assistant President of Sega Amusement Machine Research and Development Department 3 (AM3).
In 2000, "AM3" became Hitmaker, and the President of Hitmaker at the time, Tetsuya Mizuguchi, was promoted to Sega "AM9" (which became United Game Artists). This Oguchi became the President of Hitmaker.
A year later, Isao Okawa died, and Oguchi became President of Sega. But in 2004 Sammy bought a controlling share in Sega Corporation at a cost of $1.1 billion, after which Sammy chairman Hajime Satomi became President of Sega and Oguchi was shunted down into the position of Assistant President. He left Hitmaker as a result and Mie Kumagai took his place.