Asaoka was born in Tokyo Metropolis on April 6, 1962. After graduating from the University of Tsukuba, he joined Japan Soccer League club Nippon Kokan in 1985. Starting in 1985, the club won second place for three years in a row. He played 63 matches and was selected Best Eleven 1985/86. He moved to Yomiuri in 1988. The club won the league championship in 1990/91. He retired in 1991.