Kitahara trained in
soccer and
karate during high school, particularly the latter due to his penchant for
street fighting. After graduating and moving to
Tokyo, he started training
mixed martial arts at
Satoru Sayama's Super Tiger Gym and eventually became an instructor. Three years later, he developed an interest in
professional wrestling and decided to become a wrestler.
All Japan Pro Wrestling (1988–1990) Kitahara began as a trainee for
Japan Pro-Wrestling in 1987. After the promotion dissolved, he transferred to
All Japan Pro Wrestling and trained under
Genichiro Tenryu. He made his debut on April 8, 1988, against
Mitsuo Momota. He was part of Tenryu's
Revolution stable. After spending nearly a year floundering in the opening and mid-card matches, Kitahara left for Canada in March 1989. When he arrived in Canada, he joined
Stu Hart's
Stampede Wrestling in Calgary, where he used the
ring name Sumo Hara. On July 4, Kitahara was involved in a car accident near Jasper, Alberta, while riding in a car with
Ross Hart,
Davey Boy Smith,
Jason the Terrible and
Chris Benoit, which he escaped with a minor shoulder injury. In August 1989, Kitahara won his first championship, the
Stampede International Tag Team Championship with fellow Japanese wrestler
Kensuke Sasaki. The two held the championship for more than a month before losing them to
The Blackhearts. After Stampede shut down in December 1989, he returned to Japan in February 1990. Upon returning to AJPW, Kitahara was finally finding his niche, but was cut short the summer of 1990, when Kitahara joined his mentor Tenryu and
Megane Super. After leaving AJPW, Kitahara would make a brief return to Canada to wrestle for the Canadian National Wrestling Alliance as Sumo Hara, before returning to Japan for the new promotion.
Super World Sports (1990–1992) Kitahara wrestled for
Super World of Sports in 1990. As expected, he was part of Tenryu's group, Revolution. In December 1990, Kitahara took part in the original four-man tournament for the SWS Light Heavyweight Championship, but lost to
Naoki Sano in the semi-finals when a doctor called a stop to the match. After a year in mid-card tag team matches, Kitahara teamed with
Shinichi Nakano for a tournament to determine the SWS Tag Team Champions, but lost to his Revolution stablemates, Tenryu and
Ashura Hara. In June 1992, SWS folded.
WAR (1992–2000) Upon SWS's folding, Kitahara joined Tenryu in forming
WAR. Now known as Koki Kitahara, in the early years of WAR, Kitahara would be Tenryu's main tag team partner in battles against
New Japan Pro-Wrestling, but in later years, he teamed with
Koji Kitao. In September 1994, Kitahara toured Mexico for
Consejo Mundial de Lucha Libre. In April 1995, Kitahara won his first championship in Japan, the
WAR World Six-Man Tag Team Championship, with Tenryu and
Animal Hamaguchi. He won two more, with
Arashi,
Nobutaka Araya, and
Lance Storm as his partners. In 1999, WAR folded.
Freelance (1999–2018) In 1997, still as a WAR member, Kitahara formed his own mixed martial arts
dojo, Capture International. It initially developed into a
shoot-style professional wrestling promotion, which held its first card in 1998. He later expanded it into a
non-profit private security company named Japan Blue Blazer. After WAR folded, Kitahara focused primarily on Capture International, while taking select shows and tours of various promotions, including a brief return to AJPW in 2001, where he won the
All Asia Tag Team Championship with Arashi, and also with
Tenryu Project. On April 2, 2018, Kitahara announced his retirement to take place at a June 11 card promoted by AJPW dojo classmate
Kenta Kobashi, which will also be his 30th anniversary. In a tag team match, Kitahara and
Mitsuya Nagai lost to
Naomichi Marufuji and
Super Tiger II. ==Championships and accomplishments==