"All the credit to Kurumi, she played so well," Jankovic said in press after the loss. "She was playing quite solid and running a lot of balls down, she did very well from her side. And I was struggling on my own."
Jankovic recovered from a double break down in the opening set to edge past Nara in the tiebreak.
But the Japanese established herself in the final two sets, outhitting Jankovic as the Serb struggled with lower back pain, before falling after a two-hour and forty-four minute battle.
"I tried my best today but unfortunately I wasn't feeling my best out there - I had pain in my back and over time it was feeling worse and worse," Jankovic explained.
"I tried and tried to fight, but in the end it wasn't good enough. I never enjoy being on court when I'm in pain."
Nara will take on China's Zhu Lin in the second round.
No.2 seed Samantha Stosur had a more straightforward road to round two, hitting past Danka Kovinic in straight sets, 6-2, 6-4. The Australian imposed her game early on, breaking five times during the hour and twenty-one minute encounter.
The win - her first victory of 2017 and her first since the 2016 US Open - will come as a relief for Stosur after a disappointing string of first-round losses during the Australian swing.
"Well, I knew I was going to win a match at some point, so I'm more just happy that now I have. Obviously it's been a little while," Stosur explained.
"I've had a shoulder problem since US Open, but I kept practicing and playing and everything. It felt uncomfortable for a long time, but now it seems to be getting better and better."
Her next opponent will be Slovakian qualifier Dalila Jakupovic, who knocked out WTA veteran Francesca Schiavone 7-6(2), 6-3.
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This article was first seen on www.wtatennis.com.