China had withdrawn its badminton players from last week's Japan Open as tempers flared over disputed islands, putting both nations on red alert.
However, former French Open champion Li Na, Zheng Jie and Peng Shuai were all scheduled to play, Zheng and Peng in first-round matches in Tokyo on Monday.
None of the trio hit a ball in anger on Sunday's opening day, when torrential rain halted play outside with centre court matches played under a closed roof.
Slovakia's Dominika Cibulkova progressed to the second round, the 12th seed beating Spaniard Anabel Medina-Garrigues 6-3 7-6.
Fourteenth seed Roberta Vinci struggled against Czech Barbora Zahlavova Strycova before the Italian came through 6-4 4-6 7-5.
Former world number one Jelena Jankovic, who has slipped to 24th in the rankings since topping the women's game in 2008, had less trouble reaching the second round.
The Serbian looked sharp on the Tokyo hardcourt as she ousted Belgium's Yanina Wickmayer 6-3 6-3 under floodlights.
Nine of the world's top 10 are taking part in the $2.16 million Pan Pacific tournament, with only US Open champion Serena Williams missing the WTA premier five event.
Tensions between China and Japan are in danger of boiling over because of a bitter flare-up over disputed islands in the East China Sea.
Japan pulled out of the second leg of the Asian Sevens Series in Shanghai amid safety fears, while a Japanese cycling team were booted out of a race in China.
Li, who received a first-round bye, faced the press on Sunday but blanked all questions on the territorial flare-up which shows little sign of abating.
The Japanese government's decision to nationalise some of the islands -- known as the Senkaku in Japan and Diaoyu in China -- triggered angry protests across China, many turning violent.