Samantha Stosur began the defence of her Japan Women’s Open title with a hard-fought 6-4 7-5 victory over home hope Misa Eguchi.

The top-seeded Australian won 84 per cent of points on her first serve, but it still took 90 minutes for the former US Open champion to overcome Eguchi, who is ranked No.127 in the world.

Stosur advances to a second round meeting with compatriot Jarmila Gajdosova, who also saw off a Japanese opponent, Miharu Imanishi, 6-4 6-0.

Fourth seed Coco Vandeweghe needed less than an hour to beat France’s Kristina Mladenovic, the American racing to a 6-2 6-3 victory.

Awaiting her in the second round is Croatia’s Ana Konjuh, who was a 4-6 7-5 6-2 winner over Zheng Jie of China.

Kazakhstan’s Zarina Diyas, seeded fifth in Osaka, beat Chan Yung-jan 7-6 (7-3) 6-1 while eighth seed Lauren Davis also battled through to second round, ending the hopes of Japan’s Hiroko Kuwata 1-6 6-4 7-6 (7-3).

Spain’s Lara Arruabarrena and home favourites Shuko Aoyama and Misaki Doi were also first round winners on Tuesday.