Fifth-seeded Ai Sugiyama of Japan overcame compatriot Shinobu Asagoe in straight sets Tuesday to book her place in the second round of the Toyota Princess Cup.

Sugiyama wrapped up her first-round match with a 6-4, 6-1 victory while rain washed out play on the outdoor courts at Ariake Tennis Forest Park for the second straight day.

After struggling with her serve and committing a number of unforced errors, world No. 20 Sugiyama eventually found her rhythm to come back from 4-2 down and take the opening set.

Sugiyama, semifinalist at last week's Shanghai Open, then traded breaks at the start of the second set before punishing error-prone wildcard Asagoe to win the next five games and the match.

The 27-year-old, who has opted out of the upcoming Asian Games to focus on qualifying for next month's Sanex Championships in Germany, admitted that her victory had been less than convincing, despite the scoreline.

"I wasn't feeling too good out there today and if my opponent had not made so many mistakes in the second set, things may well have turned out differently," she said.

In the day's only other singles match under the center court roof, Elena Likhovtseva of Russia defeated Spain's Conchita Martinez 6-2, 4-6, 6-2.

World No. 1 Serena Williams played her first match since winning last month's U.S. Open when she teamed up with veteran Martina Navratilova in the doubles to defeat Martinez and Australian Nicole Pratt 6-1, 4-6, 6-3.

"I was having a few withdrawal symptoms from not having Venus here but if I've got to be partnered with anyone else, there is nobody better than Martina," said Williams, who had previously only ever played doubles with her sister.