Kiyoshi Kosugi was born in 1939 in Tokyo into a large, go-playing family. His parents and all six of his brothers and sisters know how to play go, and three of them---his father, mother, and younger brother---are professional go players. Under his father's tutelage, he became a professional shodan in 1957, reached 2-dan the next year, and 3-dan the year after that. In 1967 he took second place in the second division of the Oteai tournament, which determines a professional player's rank, and was promoted to 5-dan. In 1979 he came in second in the 23rd Prime Minister's Cup. He became 8-dan in 1991. Besides go, he likes to read and play mah jong. He lives with his wife and family in Chiba Prefecture.