Naomi Osaka, finding composure and grace beyond her years, somehow ignored the extraordinary meltdown of the woman who inspired her to take up the game, Serena Williams, who dissolved in tears after three code violations contributed significantly to her shock defeat in her ninth US Open final here on Saturday night.

On the 45th anniversary of Margaret Court winning her 24th and final major, Williams was favoured to move alongside the Australian in the history books but imploded in the second set – surrendering a whole game when she called the chair umpire, Carlos Ramos, “a thief” – as 20-year-old Osaka held her nerve to win 6-2, 6-4, the first ever Japanese winner of a grand slam title.

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The match itself was jam-packed with quality and rollercoaster moments, but a passage of drama at the end drowned out even those memories. It began when Osaka was 40-15 up in the second game of the second set, after Ramos gave Williams’s coach, Patrick Mouratoglou, a code violation for coaching – which the Frenchman later admitted. Williams then went 3-1 up but, exasperated over a close line call as she lost serve, she earned a second violation for smashing her racket, leading to a point penalty.

“I didn’t get coaching!” she yelled at Ramos. “I don’t cheat! You need to make an announcement. I have never cheated in my life. I have a daughter! You owe me an apology. You owe me an apology.”

He was unmoved. As was Osaka. But the atmosphere had darkened irrevocably. What might have been a celebration of greatness had curdled into a seething controversy.

Osaka, aided by the free point, drilled two unreachable forehands to hold and then broke again for 4-3. But Williams’s dialogue with Ramos continued during the changeover – and a third code violation earned her that game penalty, saving Osaka the chore of holding serve. It put the ball back in Williams’s hand at 3-5. It was then that it all went horribly wrong.

“Are you kidding me?” she yelled. “Because I called you a thief?” She called for the supervisor, Brian Earley, as the stadium erupted in boos and jeers. Williams, near tears, shouted: “This is not fair. This is not fair. This has happened to me so many times. It is not fair. It’s really not. There are lot of men out here who have said a lot worse than that. I called him a thief because he stole a point from me. That is not right, and you know it. I know you can’t change it. I get the rules, but I’m just saying it’s not right.”

Calling on every ounce of her genius and hitting the ball with undisguised venom, she held to love inside a minute. But, even as she prepared to receive Osaka’s serve, the tears would not stop. Her sense of indignation was palpable.

Osaka threaded a forehand inside the deuce line: 15-0; Williams retrieved with an impossible cross-court winner: 15-all; Williams netted a return: 30-15; Osaka aced, 113mph: 40-15. Williams struck an unreachable backhand to the advantage corner: 40-30; Osaka hit a serve that Williams did well to even get a racket on: game, set, championship.

Mouratoglou later admitted to the host broadcaster, ESPN: “I’m honest. I was coaching. But I don’t think she was looking at me. We have to stop this hypocrisy. Sascha [Bajin, Osaka’s coach] was coaching too. She shouldn’t have to think about that. She should be able to express her emotions. She’s human. It’s not a big deal breaking a racket. Not once in my life have I been penalised for a coaching violation.”

Facebook Twitter Pinterest Naomi Osaka lifts her trophy after defeating Serena Williams to claim her first grand slam title. Photograph: Anadolu Agency/Getty Images

During the on-court presentation, with a mix of cheers and jeers among the 23,000 fans present, Williams fought for some calm and said: “I don’t want to be rude. She play well. This is her first grand slam. Let’s make this the best moment we can. Let’s give everyone credit where it’s due. Congratulations Naomi. No more booing.”

Osaka rescued the moment from total farce when she said: “I know everyone was cheering for her ... I’m sorry I’m like this [crying]. I just want to say thank you for watching the match. My mum sacrificed a lot for me and it means a lot for her to come and watch – because she doesn’t normally come. All that was missing my dad, but he doesn’t watch, either. It was always my dream to play Serena in the US Open final, and I’m really grateful I was able to do that.”

A script writer could not have crammed more scenarios into the hour and 19 minutes it lasted. Osaka, born in the city that bears her mother’s name, went to school half an hour from this venue, after her Haitian father and Japanese mother arrived in the United States 17 years ago. She then followed a well-worn trail to Boca Raton in Florida to pursue her career, inspired by Williams.

Bajin, Williams’s training colleague for eight years whom she always considered “much more than a hitting partner”, now coaches Osaka and, in their first year together, has helped her move from No 68 in the world to 19.

In their only meeting on court, Osaka, coming off her tour debut triumph in Indian Wells, caught Williams at the right time of her comeback and beat her 6-3, 6-2 in the first round in Miami. Two hours before this match, Osaka sat down and watched that victory again.

Lachrymose theatre aside, Osaka won this on merit. Williams, who became a mother for the first time a year ago, turns 37 this month. They might meet a few times yet.