Naomi Osaka says winning the US Open last month was a “bittersweet” moment and “not the happiest memory” following Serena Williams’ on-court outbursts.

The 20-year-old became the first Japanese player to win a Grand Slam when she beat the American 6-2 6-4.

But the final at Flushing Meadows was overshadowed when Williams called umpire Carlos Ramos a “thief” and later accused him of sexism.

“There’s a lot of stuff I want to say about how I felt,” said Osaka.

“For me, I don’t know, I don’t know, the memory of the US Open is a little bit bittersweet.”

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• Umpire Carlos Ramos defended by ITF after Serena Williams row

World number six Osaka has always refused to point the finger at 23-time Grand Slam champion Williams, 37, but said she had immediately wanted to “move on” following her win in New York.

“Right after, the day after, I really didn’t want to think about it because it wasn’t necessarily the happiest memory for me,” she said. “I just sort of wanted to move on at that point.

“Of course I’m happy that I won a Grand Slam, I don’t think there’s anything that can take away from that, but I feel like it was so strange, I didn’t just want to think about it.

“I wanted to just push it to the side.”

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British number one Kyle Edmund fought back from a set down to reach the second round of the China Open with victory over Peter Gojowczyk.

Fifth seed Edmund won 3-6 6-1 6-2 in 91 minutes in Beijing against the world number 70 from Germany.

Edmund will face Italian qualifier Matteo Berrettini or Argentina’s Leonardo Mayer next.

The world number 16 is playing his first competitive event since his US Open first-round loss in August.

The 23-year-old has had a tough year because of illness, including recurring bouts of tonsillitis.

Before heading to China, he helped Team Europe beat Team World in the Laver Cup exhibition event in Chicago at the end of September.

Edmund was broken in his first service game against Gojowczyk, falling 3-0 behind following several unforced errors, before responding to get the set back on serve at 3-2.

But Gojowczyk broke again for a 5-3 lead, eventually converting his first set point with an ace after 31 minutes.

Edmund, though, broke the German three times in the second to force a decider after converting the second of three set points with an ace.

The Briton claimed the key break for a 3-2 lead in the third set before pulling clear to seal victory at the first opportunity with an ace.

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Elsewhere, seventh seed Borna Coric lost 7-5 5-7 7-5 to Spanish wildcard Feliciano Lopez, while American Sam Querrey was beaten 6-4 6-4 by Russia’s Karen Khachanov.

In the women’s event, two-time Grand Slam champion Garbine Muguruza from Spain beat Russia’s Ekaterina Makarov 6-0 6-4.

At the Japan Open, world number 12 and two-time champion Kei Nishikori beat Japanese compatriot Yuichi Sugita 6-4 6-1 in the first round.

Three-time Tokyo finalist Milos Raonic from Canada beat 2017 runner-up Adrian Mannarino from France 6-3 6-4.