The 20-year-old melted hearts when she broke down sobbing after thrashing her idol 6-2, 6-4 to become Japan's first Grand Slam singles champion in NY last weekend.
Osaka already earns a six-figure salary with Adidas, which is due to expire at the end of the year.
"At the time, I did kind of think they were booing at me".
"I just thought I shouldn't have any regrets".
Despite collecting just $62,000 between June 2017 and June 2018 due to a break to have her daughter Olympia, Williams earned $18.1 million to be the world's top-earning female athlete thanks to a lucrative endorsement portfolio.
"I guess I'd like to hang out with my sister - I haven't seen her since Wimbledon", said Osaka, who has become an unlikely hero in a country still reeling after a summer of deadly typhoons and earthquakes.More news: Victims honored at 9/11 Flight Crew Memorial in Grapevine
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But after returning to Japan on Thursday, Osaka insisted there were no hard feelings towards Williams, who branded umpire Carlos Ramos a "thief" in an astonishing tantrum triggered by a code violation for coaching that culminated in a docked game. The 23-time Grand Slam victor was later fined $17,000 for her behavior.
But before that, Osaka appeared on The Ellen Show, hosted by Ellen DeGeneres, who tried to set her up with her crush, Black Panther star Michael B. Jordan.
The Japanese star said she tried to ignore the furore as it was unfolding around her because that was what she had been taught to do since she was a child.
(AAP)Serena Williams embraces Naomi Osaka after the US Open women's final.
"But in my mind, I was sort of, I really wanted to know what was going on". The brand is always challenging expectations, and I look forward to bringing its vision for driving excitement to new audiences around the world'.
"I was looking away, but I heard a lot of people in the crowd making noises, and I really wanted to turn around, but I didn't", Osaka said.