Yokoyama Koichi

横山孝一 Yokoyama Kōichi (1919–2005) Nihon Ki-in professional, 6 dan in 1977. Close friend of the late Kageyama Toshiro, they collaborated on the book Kage's Secret Chronicles of Handicap Go.

He became a professional shodan in 1951, a 2-dan in the same year, As a player, he reached 6-dan. In 2001, he retired, with promotion to 7-Dan.

Passed away on December 18, 2005, receiving posthumous promotion to 8-Dan.