Naomi Osaka takes the title, and finds her voice in new career chapter
As well as winning Grand Slams, Japan's biracial star is making sure tennis fans know how she feels about social injustice.
Naomi Osaka is a three-time Grand Slam winner.
At 22, she was already sport's highest-earning woman, having also become Asia's first tennis world number one, and will be among the favourites for gold at next year's Tokyo 2020 Olympics.
But this latest success has been marked by her desire to bringing awareness of racial inequality to the forefront of tennis, marking a clear new chapter in Osaka's career.
Sibling rivalry and the makings of a champion
Osaka was born in Chuo-ku, Osaka to Japanese mother Tamaki Osaka and Haitian father Leonard Francois in October 1997.
The family moved to New York's Long Island in 2000 with Francois following the example of Richard Williams, the father of Venus and Serena Williams, by teaching Naomi and older sister Mari to play tennis.
Six years later they moved to Fort Lauderdale in Florida with the girls being homeschooled in the evening after playing tennis during the day.
Mari is also a professional, with a career-high ranking of 280, and younger sister Naomi admitted to CNN in 2019 that finally beating her sibling in March 2014 was a pivotal moment.
"If she wasn't there I wouldn't be where I am right now. Growing up there was always the two of us and I would always get inspired by her and she would constantly beat me, so that was kind of a very big motivation for me. She beat me probably more than 1,000 times over my childhood."
"It took 12 years to beat her. It was probably one of the biggest moments of my career. I went home to my mom and I was bragging." - Naomi Osaka to CNN on finally beating big sister Mari
Like the Williams sisters, Osaka opted to play in pro-satellite tournaments rather than junior events.
Her breakthrough came in the 2014 WTA Stanford Classic where both siblings were in the qualifying draw.
While Mari went out in her opener, Naomi defeated a WTA Tour title winner in Alla Kudryavtseva and a beaten finalist in Petra Martic to reach the main draw.
Then came a stunning victory over 2011 US Open champion Samantha Stosur, after the Australian had taken the first set.
Defeat to Andrea Petkovic followed, but Osaka had made her mark.
Osaka was also runner-up on grass at Surbiton, going down in the final to Russia's Vitalia Diatchenko, before suffering defeats in qualifiers for Wimbledon and the US Open to Sorana Cirstea and Jo Konta respectively.
Her performances saw her earn a place in the WTA Rising Stars Invitational in Singapore, an exhibition tournament on the undercard of the WTA Finals, where she defeated top seed Caroline Garcia in the final.
Breaking into the big time
Osaka really started to make strides in 2016, reaching her first Slam main draw at the Australian Open and stunning 21st seed Elina Svitolina before going out to Victoria Azarenka.
A win over world no.18 Sara Errani at the Miami Open propelled her into the world's top 100 for the first time and thereby gain main draw entries to Slam tournaments.
In the French Open, she won two matches before taking the opening set against sixth seed Simona Halep.
The Romanian came back to win but Osaka's season was interrupted by injury which forced her to miss the grass court season.
Then in September came a stunning performance at the Pan Pacific Open in Tokyo as Osaka defeated sixth seed Dominika Cibulkova and Svitolina again to become the first Japanese player to make the final since Kimiko Date in 1995.
Caroline Wozniacki proved too strong in the final, but Osaka had shown enough to suggest that titles would be coming her way before too long.
While 2017 failed to follow the same rapid trajectory of the previous year, despite her first top-10 wins over Angelique Kerber and Venus Williams, 2018 was a different story.
New coach Sascha Bajin was the catalyst, with Osaka reaching the fourth round of the Australian Open, her best showing at a Slam thus far, before going out to world number one Halep.
Then came her first WTA Tour title, and a Premier Mandatory event to boot, at the Indian Wells Open.
In Miami the following week, Osaka defeated Serena Williams at the start of her comeback following childbirth.
There followed something of a slump in form including third-round exits at the French Open and Wimbledon, the latter to eventual winner Kerber.
But it all came together at the US Open as the top 10 seeds all failed to make it past the quarter-finals.
Osaka took full advantage, dropping just one set on the way to the semi-finals where she brushed aside Keys in straight sets.
Then came the final against Serena Williams which should have been her toughest test.
In the end, the youngster was a convincing winner although her 6-2 6-4 victory was overshadowed by Williams' tirade at umpire Carlos Ramos after he gave her a code violation for illegal coaching.
Osaka's triumph saw her become Japan's first Grand Slam winner, male or female.
Osaka then made it back-to-back Slam victories in the 2019 Australian Open despite being in trouble in several matches en route to the final.
She defeated Petra Kvitova to become the first Asian player to reach the top of the world rankings, but then announced she was splitting with coach Bajan telling Reuters, "I wouldn't put success over my happiness."
Replacement Jermaine Jenkins lasted less than six months as Osaka struggled, but having her father back as her coach sparked a return to form with consecutive tournament victories at the Pan Pacific Open and the China Open.
She linked up with Wim Fissette, former coach to Kim Clijsters, Azarenka, Kerber, and Halep among others, at the start of the 2020 season and things did not click immediately.
The defence of her Australian Open title ended in a third-round loss to teenage sensation Coco Gauff, and a one-sided Fed Cup loss to Spain's Sara Sorribes Tormo in February was her last match before the suspension of the WTA Tour due to the COVID-19 pandemic.
But since then, and perhaps driven by the racial injustice she has spoken about in the United States, only injury has been able to stop Osaka who pulled out of her Cincinnati Open Final with Azarenka due to a left hamstring injury.
When they did finally meet in the US Open Final, it was Osaka - wearing strapping on that left thigh - who came out on top after an almighty battle.
Osaka was below her best in the first set with Azarenka, seeking to become the first mother since Clijsters to win a Grand Slam title, racing through it 6-1.
The Belarusian broke to lead 2-0 in the second set but then Osaka upped her game in spectacular fashion.
After some exceptional baseline rallies, it was the Japanese who powered ahead to take it 6-3 and level the match.
She broke early in the decider but Azarenka - whose level had only dropped slightly in the second set - showed great tenacity to claw her way back into it.
But Osaka then broke again for a 5-3 lead before serving out for her second US Open title.
What the match proved emphatically is that when she is on song, there is very little anyone can do about it.
From shy teenager to leader
Osaka is one of the most prominent biracial personalities in Japan.
Lucrative endorsements following her first two Grand Slam wins saw her eclipse Serena Williams to become sport's highest-earning woman in 2019.
Having grown up in the United States, she does not speak fluent Japanese but does understand the language well.
After her 2019 Australian Open win, she was asked a question in Japanese but replied in English.
It prompted a flurry of headlines as well as an, admittedly positive, opinion piece in the Japan Times entitled 'How Japanese is Naomi Osaka?'
Of course, Osaka will be one of the headline acts at next year's postponed Tokyo 2020 Olympic Games where she will hope to win gold for the home nation.
As well as her incredible play, Osaka had been known for her shyness in interviews.
Her victory speeches often suggested slight embarrassment and unease at her fame and having to speak publicly.
But during the COVID-19 break, she gave notice that things were about to change.
Osaka keen to make impact beyond tennis
Last month, Osaka joined NBA players in going on strike, after the police shooting of Jacob Blake in Kenosha, Wisconsin.
She refused to play her semi-final at the Cincinnati Open - held in New York - with the WTA and ATP then backing her stance by suspending play for the day.
Osaka explained why she went on strike on social media saying, "As a black woman I feel as though there are much more important matters at hand that need immediate attention, rather than watching me play tennis."
After winning her rescheduled match against Elise Mertens, she told ESPN, "Honestly, I’m more of a follower than a leader. I was just waiting and waiting, and then I realised I would have to be the one to take the step."
At the US Open, she wore facemasks ahead of each match bearing the names of black victims of police brutality or racially-motivated shootings including George Floyd and Breonna Taylor.
Osaka had seven masks and needed all of them as she claimed her second US Open title.
On court afterwards, she said, "I feel like the point is to make people start talking. I've been inside of the bubble so I'm not really sure what's really going on in the outside worId. All I can tell is what's going on on social media and for me, the more retweets it gets - that's so lame - the more people talk about it."
In response to video messages of support from parents of two of the victims - Ahmed Arbery and Trayvon Martin - an emotional Osaka told ESPN, "It's extremely touching that they would feel touched by what I'm doing. For me, I feel like what I've doing is nothing. I'm really grateful, and I'm really humbled.
"I feel like I'm a vessel, at this point, to spread awareness and hopefully I can help." - Naomi Osaka to ESPN
The Black Lives Matter movement in the country she has spent most of her life has clearly motivated Osaka to become more vocal, leading to her highlighting social injustice.
Being in a COVID-secure 'bubble' at the US Open, she thought facemasks would be the best way to raise awareness of discrimination against black people.
She told ESPN, "I'm hoping people will Google the names to find out more. People are watching this tournament globally; I just want to do my part to raise awareness.
"I realised that no one else was speaking up, so, as a black woman, I felt it was time for me to speak up."