Koyama, seeded joint fifth, was scheduled to meet the Latvian Olga Kartuzova. "She has not been well for nearly a month. She has been coughing and also has some back trouble," a Japanese official said.
Despite not being fully fit, Koyama, formerly known as He Zhili, won all her seven matches in the team competition in which Japan finished sixth and was considered one of the few challengers to China's grip on the women's title. China have already retained both team trophies in their attempt to repeat the 1995 clean sweep of all seven golds.
Kong Linghui opened the defence of his men's title in convincing fashion against the left-handed Dutchman Jorg de Cock, ranked 277 places below the champion.
It was a match of staccato rallies with both players manoeuvring for the third-ball kill. The 21-year-old Kong coasted to victory 21-13, 21- 9, 21-18, and the only time he had to dig deeper into his impressive repertoire of strokes was when he trailed the workmanlike De Cock 7-12 in the third game.Reuse content