Olympic champion Monica Puig bounced back to winning ways with a comfortable straight-sets victory over Varvara Lepchenko in Tokyo.
The 22-year-old claimed the gold medal in Rio but was then dumped out of the US Open in the first round by China's Saisai Zheng.
However, she was back on form at the Toray Tennis tournament and was rarely troubled by the Ukrainian-born American, claiming a 6-0 6-3 success.
The world number 34 needed only 74 minutes to book her place in round two, while wild card Naomi Osaka won the battle of the Japanese players to beat Misaki Doi 6-4 6-4.
There is plenty of action in the Far East this week, with the Guangzhou Open in China also taking place, and Croatian third seed Ana Konjuh opened with a 6-2 6-2 win over Tatjana Maria of Germany.
Fifth seed Alison Riske beat Chinese qualifier Fang Ying Xun 6-3 6-3 and sixth seed Danka Kovinic took care of another Chinese player, Yafan Wang, 6-3 6-4.