In contrast to Osaka's comfortable win, Pliskova dropped the second set before sealing a 6-2 4-6 6-3 victory in a match that lasted more than two hours.
Pliskova's win ends an incredible run by Osaka that saw her take the U.S. Open and roar through the Pan Pacific draw unscathed as the buzz over her grand slam win reverberated across the country.
The 20-year-old Osaka has signed with the US$500,000 Hong Kong tournament to make her second straight appearance at Victoria Park and was scheduled to compete in this week's Wuhan Open in China. Just after winning the US Open, where she pulled off a major upset by beating Serena Williams 6-2 6-4 under controversial circumstances. "Naomi was playing so good all tournament but I think she was a little bit exhausted today".
"It was another long one today!"
Osaka's victory in front of an expectant home crowd was her 10th in a row and did not look in doubt from the moment the world number seven pounded down a huge ace with her first serve of the match.
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"I didn't want to try to overpower her because I think she just has more power than me, so I just wanted to be patient and just to wait for my chances, waiting for my shots", Pliskova said. "She was missing quite a lot today so it was working, so I didn't change anything". The Japanese, who played the first of her four finals here in 2016, could have become the youngest champion here since 2010.
"I've never felt more exhausted in my entire life", she said, admitting that a much-needed rest was in order. Meanwhile, Osaka advanced to the third round and had Madison Keys on the ropes before the American rallied for the win. "Naomi was maybe a little bit exhausted, you could see that.
Even when it's not working, I know it can work the next day", said former world No. 1 Pliskova, who praised third-seeded Osaka for her play throughout the tournament. "So if there is anything I can take from this it is that I am proud of myself".
She broke the eighth-seeded Strycova to take a 3-1 lead in the first set but was soon broken back.
Currently just outside the eight qualifying spots for next month's WTA Finals in Singapore, Pliskova has now spent 420 minutes on court in Tokyo compared to 222 minutes for Osaka.