The 36-year-old is back in the final in NY for the first time in four years and one step away, as she was at Wimbledon, from equalling Margaret Court's all-time record for slam singles titles.
Minori Nakano, a teacher and translator from the city of Kobe in western Japan, praised 20-year-old Osaka's after-match comments in English as "so cool and yet so Japanese".
Responding, Williams said: "I literally just heard that too".
"You owe me an apology", Williams said.
"It was always my dream to play Serena in the US Open finals".
"I felt like I shouldn't let myself be overcome by nerves or anything, and I should just really focus on playing tennis because that's what's gotten me to this point", Osaka said.
The second code violation cost Williams a point, meaning Naomi Osaka had a 15-0 even before hitting her first serve in the sixth game of the second set.
Another chance came and went in the eighth game and, although Keys was now serving superbly, she just could not find a way through.
Asked in her press conference what she would have done differently in hindsight, Williams became increasingly emotional as she said: "I can't sit here and say I wouldn't say he's a thief, because I thought he took a game from me". Then she got a point penalty for smashing her racket and finally earned a game penalty at 4-3 down for a verbal attack, calling Ramos a "liar" and a "thief".
Serena Williams argued with a chair umpire during the U.S. Open finals who gave her several penalties, telling him "I don't cheat to win, I'd rather lose".
"She fought for her life, for our child, for recognition, for equal pay, for women's rights".
Serena Williams's husband Alexis Ohanian celebrated her return to the US Open final with a touching Twitter tribute interspersing video of her on-court exploits and the first days of their daughter Olympia a year ago.
"There are matters that need to be looked into that took place during the match", said the WTA. "I wasn't being coached".
Q: You're on a very short list of people who have beaten Serena in their first two matches against her.
"I'm not at liberty to talk about it". I haven't cheated in my life. "Maybe it didn't work out for me, but it's going to work out for the next person".
Osaka also has a strong attachment to Japanese culture, describing her visits to the country as like a "super-awesome extended vacation that I don't want to leave", according to media reports.
Despite what Serena did on the court, a moment of class prevailed as she comforted Osaka and told fans to quit their booing. Williams quickly tried to squash that ridiculous notion, but the ump continued to make accusations, and now we have plenty of entertaining audio from it all.
Williams objected right away, saying she would never cheat.
Williams streaked into the US Open having won the Australian Open and Wimbledon that year and chasing a second straight title in Flushing Meadows.
Japan has been charmed by Osaka's off-court humility and genuineness as much as her on-court ferocity and that unpretentiousness came through in her post-match comments.
Even with all the chaos around her, Osaka managed to stay poised and close out the win.
Williams hasn't won the U.S. Open since 2014 and hasn't won anywhere since the 2017 Australian Open, when while pregnant she became the oldest Grand Slam female champion at 35.