Mezue ahịrịokwu na-esonụ: A mụrụ Koga na Kitashigeyasu, Saga, Japan. Ọ malitere ịgba judo n'ụlọ akwụkwọ praịmarị. Ọ gara Tokyo n'oge ụlọ akwụkwọ sekọndrị iji banye Kodogakusha, ụlọ akwụkwọ judo nke ndị mmeri ọla edo n'egwuregwu Olympic Hidehiko Yoshida na Makoto Takimoto mechara gaa. Ọ gara n'ihu agụmakwụkwọ ya na Mahadum Nippon Sport Science, wee nweta ọtụtụ ihe nrite gụnyere mmeri ise na-esote na Kodokan Cup na mmeri isii na-esote na All-Japan Judo Championships (niile na ngalaba 71 kg). O tinyere nke atọ na 1987 World Judo Championships nke emere na Essen, ma họrọ ya isonye na 1988 Summer Olympics, ebe o meriri na agba nke atọ nke asọmpi ahụ. Koga laghachiri n'egwuregwu Olimpik n'afọ 1992 mgbe o meriri asọmpi
1989 na 1991 World Judo Championships, mana merụrụ ahụ ikpere aka ekpe ya n'oge nnọkọ randori (na-agba ọsọ) megide Hidehiko Yoshida, nke gbochiri ya iji usoro kachasị mma ya; Ippon Seoinage. O meriri ihe nrite ọla edo na-emeri mmerụ ahụ a, ma nye JOC Sports Award site na Kọmitii Olimpik Japan.