Shinzo Abe and Japanese news outlets have lauded Naomi Osaka’s victory at the US Open on Sunday

While the tennis world debated the merits of Serena Williams’ tirade against umpire Carlos Ramos during Saturday’s US Open final, Japan heaped praise on its first grand slam winner, Naomi Osaka.

The 20-year-old remained composed to beat Williams in straight sets, only to see her historic achievement overshadowed by the fallout from her opponent’s claims that she had been the victim of sexism from the umpire’s chair.

But Japanese social media lit up with messages of congratulation, including one from the prime minister, Shinzo Abe, who congratulated Osaka on Twitter and thanked her for “giving Japan a boost of energy and excitement at this time of hardship” – thought to be a reference to a barrage of natural disasters that have together killed hundreds of people and caused widespread damage in Japan in recent weeks.

Her compatriot and defeated US Open semi-finalist, Kei Nishikori, tweeted his support, largely in emoji form.

Osaka’s grandfather, Tetsuo, told reporters at his home in Hokkaido, that he and his wife were “ecstatic” after watching their granddaughter’s 6-2, 6-4 victory over Williams on television.

Japanese media also responded positively to the win. The Yomiuri Shimbun, a conservative broadsheet, said: “The combination of her strength and childlike innocence is her charm,” and hailed Osaka as “a new heroine Japan can be proud of.”

The large contingent of Japanese journalists at Flushing Meadows largely ignored the Williams-Ramos spat, choosing instead to ask Osaka about her multicultural heritage, and what she would like to eat for her first meal as US Open champion. To which she gave the crowd-pleasing answer: katsu curry.

Tennis fans who had woken up early to watch the final live on cable TV were particularly impressed that Osaka appeared unfazed by the confrontation between Williams and Ramos.

Play Video 0:51 Serena Williams calls umpire a 'liar' and 'thief' as Naomi Osaka wins US Open final – video

“She remained so calm throughout the match despite all that,” said Mitsuko Sakai, an amateur tennis player. “I was very impressed by her mental strength. The entire crowd seemed to be cheering for Serena, but Osaka concentrated on the game and won.”

After widespread coverage of her win in newspapers and on TV, Osaka may see her efforts rewarded with lucrative commercial deals as Japan prepares to host the Olympics in two years’ time.

The combination of her strength and childlike innocence is her charm Yomiuri Shimbun

Osaka, who was born in the city of Osaka (although the second half of their names are written using different kanji characters) to a Japanese mother and Haitian father, moved to the US when she was three and was raised in Florida.

Her victory has raised hopes that the country of her birth will adopt a more inclusive definition of Japanese identity in a society that often sees itself – with increasing imprecision – as racially homogenous, and where mixed-race people are routinely referred to as haafu (half).

Osaka, who holds dual Japanese and American citizenship, is one of several mixed-race athletes who represent Japan – where one in 50 children are born to international couples – along with the US Major League baseball player Yu Darvish, whose father is Iranian, and the Olympic sprinter Asuka Cambridge, whose father is Jamaican.

“Japanese are becoming more accustomed to people from other cultures,” said Hirotaka Matsuoka, a professor of sports marketing at Waseda University. “If an athlete isn’t half-hearted and really makes it clear they are representing Japan, then the public will support them.”

Agencies contributed to this report.