Genji Kaku/Yuen-chih Kuo (Kaku Genji/Kuo Yuen-chih, 郭 源治, born October 4, 1956), is a Taiwanese former professional baseball player from Taitung, Taiwan. His family comes from the Taiwanese aborigines. He obtained Japanese citizenship in September, 1989, and holds dual Japanese/Taiwan citizenships since 1999. While in Japan, he often uses the Japanese name, 佳久 源治.
Kaku first traveled to Japan in 1969 as part of the Taiwanese little league team, where his team won the little league championship. Kaku finished his military service in Taiwan, and joined the Chunichi Dragons in mid-1981. He was not regarded as a star player at that time, and arrived in Japan with only about 3000 yen (roughly $30) in his pocket.
His sharp fastball (hit 94 mph) and breaking pitches quickly earned him a spot on the starting rotation, and he won over 10 games from 1983 to 1986. However, he also lost over 10 games each of these seasons due to poor run support.
In 1987, Dragons closer Kazuhiko Ushijima was traded to the Lotte Marines for Hiromitsu Ochiai, and manager Senichi Hoshino chose Kaku as the new closer. Kaku was a huge success in the closing role, using his solid control and hard screwball to lead the Central League in saves in 1987 and 1988. The Dragons won the league championship in 1988, and Kaku received the league MVP award despite having to return to Taiwan during the season to mourn for his younger brother, who had died in a car accident.
Kaku obtained Japanese citizenship in 1989, and has a Japanese wife. He returned to the starting rotation in 1990, winning 13 games in 1991. He became a reliever in 1993, and became the fifth Japanese player in history to record 100 wins and 100 saves in 1994. He also led the league with a 2.45 ERA that year. He played his final season in Japan in 1996.
Kaku played in the Chinese Professional Baseball League from 1997 to 1999. He also participated in the preliminary rounds of the 2000 Summer Olympics with the Taiwanese national team in 1999 at the age of 42.
He has been serving as the head consultant for the Chinese Professional Baseball League since 2013.