全日本柔道選手権大会
Okada began judo in primary school, and won the inter-highschool light heavyweight judo tournament in 1984. While attending the University of Tsukuba, he won the Jigoro Kano Cup in 1986 and the All-Japan Judo Championships in 1987 and 1988, followed with a gold medal in the -78 kg division of the World Judo Championships in 1987. This earned him a spot on the Japanese olympic judo team for the 1988 Summer Olympics, but he was unable to win a medal after a loss in the third round of the tournament.