Osaka started off in style defeating Petra Kvitova in a 7-6, 4-6, 6-4 win in two hours and 39 minutes.
The Japanese ace claimed the same result as the Australian Open final in January when she claimed her second Grand Slam title.
This time though she won the first set from a break down, losing the second with a break up and then cruising through the third. It was a first WTA Finals victory for her on a third match point with 30 winners to 29 unforced errors the main stats to call on.
With it being group format, she still has to play Ashleigh Barty and Belinda Bencic who faced off in the other tie.
It was the Australian who came out on tops and she will definitely be the Year End World No.1 come what may.
Barty lost the first set but bounced back to cruise past the No.7 seed in a 5-7, 6-1, 6-2 victory in one hour and 57 minutes in the second match.
It was an intriguing tie due to both being debutants and both being two of the most in-form on the WTA circuit this season but it was Barty that came out on top hitting 30 winners and ending Bencic's four match winning streak.
The turning point came towards the end of the tie for Barty who pounced on a dead net cord on break point which saw her go 2-1 up and unforced errors came from Bencic allowing the former to claim victory with 77 percent on first serves. It was sealed with an ace on second match point as she showed herself as being potentially the player to beat and justifying that number one spot.
https://twitter.com/WTA/status/1188416211974967306?s=20
https://twitter.com/WTA/status/1188450681780178944?s=20