Yamaguchi won the All-Japan Judo Championships 10 consecutive times from 1978–1987 (twice in the -50 kg division, seven times in the -52 kg division) and won her first medal at the 1980 World Judo Championships. She went on to win 4 silver medals and one gold medal at the World Judo Championships. She also won a bronze medal in the -52 kg division at the 1988 Summer Olympics in Seoul, where women's judo was held as a demonstration sport. She retired from competitive judo in 1989 when she graduated from the University of Tsukuba. She worked as an instructor for the University of Tsukuba and Musashi University since retiring.　Yamaguchi is currently Associate professor of Tsukuba.