Down 3-4 in the set, Williams told Ramos, "You stole a point from me and you are a thief". Tom, thank you for joining us. "I'm really grateful I was able to play with you".
Osaka won her first career title at Indian Wells this year but had never beaten Keys before in three attempts and lost to the American at Flushing Meadows in 2016.
Osaka apologized to the crowd.
"I love you, Serena", she added before adding "I love you, mom; I love everybody". Williams was given a warning in the second game of the second set after chair umpire Carlos Ramos ruled she had received on-court coaching.
Naomi Osaka remembers watching Serena Williams from the stands as a 5-year-old, as well as coloring a school report on her idol in third grade. I don't cheat to win. There was no thumbs-up sign. "I mean I don't think she looked at me so that's why she didn't even think I was but I was like 100 percent of the coaches on [sic] 100 percent of the matches". He also said everyone does it and usually is not called for it.
That was the tipping point and Osaka wrapped up the win in one hour, 26 minutes with a service victor, breaking into a smile as the ball flew off the frame of Keys' racquet and into the crowd. But Williams played a poor game right after that to get broken immediately, and she smashed her racket on the court, destroying it. "And her words after the match deserve a big warm applause under the unexpected circumstances".
That cost her a point, because of the earlier warning for coaching.
Williams continued protesting to Ramos during a changeover but returned to break Osaka's serve to go 3-1 up in the second set. I'm just a tennis player playing another tennis player.More news: Bears sign Khalil Mack to record-breaking contract extension
"I know everyone was cheering for her and I'm sorry it had to end like this", she said. Tell me about her very, very briefly. How dare you insinuate that I was cheating... Ramos interpreted the remark as verbal abuse, and awarded a game to Osaka, putting the eventual victor one game away from victory.
Williams overwhelmed Anastasija Sevastova 6-3 6-0 to reach her 31st grand slam singles final. She pleaded her case through tears to the two of them, insisting she is always treated unfairly at this event - and that men have called umpires much worse and not been penalized - but there was no budge in the score.
Mike Bryan broke a tie for most major doubles titles with John Newcombe, and at 40 years, 4 months became the oldest Grand Slam doubles champion in the professional era.
Gauff won the French Open girls' title and was trying to become the first American to win two Grand Slam girls' singles titles in the same year since Jennifer Capriati in 1989.
She will now meet 23-time slam singles champion Williams, who won her first title in NY 19 years ago and thumped Anastasija Sevastova prior to Osaka's win over Keys on Thursday.
Canadian fan Vince Degiorgio, who lives in Ontario with his Japanese wife, said that Osaka's win "will be an inspiration to not only Japanese female tennis players, but all kids of mixed race people in Japan who strive to show pride in their heritage".
'There are matters that need to be looked into that took place during the match.