Japan is celebrating its first ever Grand Slam tennis win after Naomi Osaka's US Open win over Serena Williams 6-2 6-4 at Flushing Meadows on Saturday.
Osaka stayed calm as Williams went into meltdown after the umpire imposed a series of penalties.
She was later in tears waiting to be given her trophy as the partisan crowd booed the match officials, according to a BBC report Sunday.
The 20-year-old was born in Japan to a Japanese mother and a Haitian father but was raised in the US.
Prime Minister Shinzo Abe congratulated Osaka on Twitter, thanking her for "giving Japan a boost of inspiration at this time of hardship" - an apparent reference to last week's Hokkaido earthquake in northern Japan that killed more than 20 people.
Tennis is less popular than other sports such as baseball, football, and sumo wrestling in Japan, but after her win the Yomiuri newspaper said Osaka was a "new heroine Japan can be proud of".
"The combination of her strength and childlike innocence is her charm," the newspaper said.
Osaka faced hostility during what should have been a moment of joy as boos and whistles rang out around the Arthur Ashe stadium, and lowered the visor she had been wearing to hide her tears.
Williams then put her arm around her and said: "Let's make this the best moment we can, let's give everyone the credit where credit's due and let's not boo any more."
"I know everyone was cheering for her and I'm sorry it had to end like this," said Osaka. "I just want to say thank you for watching the match."
She said it was "always my dream to play Serena in the US Open finals," and, addressing her opponent, she said: "I'm really grateful I was able to play with you."
She then bowed, to applause from the crowd.
Osaka - who also holds US citizenship - is the latest dual heritage athlete to rise to prominence in Japan, which has traditionally viewed itself as an ethnically homogenous society.