Rikako Ikee brought the home crowd to its feet with victory over Olympic champion Sarah Sjostrom in the 100m butterfly at the FINA World Cup Tokyo.
The 19-year-old, who won six golds at this year's Asian Games in Jakarta, smashed her own short course national record with a time of 55.31 seconds, seven-tenths outside Sjostrom's world best.
Swede Sjostrom was a quarter of a second behind with China's Zhang Yufei finishing third.
Sjostrom also took third in the 100m freestyle behind triple Olympic champion Ranomi Kromowidjojo and her Dutch team-mate Femke Heemskerk.
Born in the Japanese capital, Ikee won the 50m and 100m butterfly titles at the 2015 World Junior Championships.
She qualified for four individual events at Rio 2016 - 50m, 100m and 200m freestyle, and 100m butterfly - and made three relay teams.
Ikee's best showing came in the 100 fly where she broke her own national record in the heats, before doing so again with a blistering second 50 metres to win her semi-final.
In the final, she finished fifth behind Sjostrom who set a world record of 55.48 which stands to this day.
But this year has seen Ikee make big waves in the international senior ranks.
She became the first swimmer to win six gold medals at an Asian Games, also taking home two silvers.
Ikee's haul saw her named Asian Games MVP, a first for a woman.
After her success in Indonesia, she spoke of her ambition to beat Sjostrom's 100 fly world record.
"It's my goal and it's important to work harder to achieve it from now on." - Rikako Ikee on Sarah Sjostrom's 100m butterfly world record
"If everything goes well, I think I will be able to break the world record. But at the same time, I don't think it will be easy."
The closest she has come so far is 56.08 seconds, six-tenths outside Sjostrom's mark, set at August's Pan Pacific Championships in Tokyo.
Being a Tokyo native, there will be massive expectation on her shoulders ahead of the 2020 Olympic Games.
But she insists she can use the support as a positive way.
"I don't feel pressure too much. For me, I gain extra power from people cheering. I love swimming, so when people cheer for me so much I feel really happy."
Ikee actually spent two weeks training with Sjostrom and her Energy Standard team in Turkey in October.
Judging by her swim in Tokyo, that trip looks to have paid off.
Xu breaks 100 back world record
The other highlight of the event was Chinese swimmer Jiayu Xu setting a new world best in the men's 100m backstroke.
Rio 2016 silver medallist Xu was more than three-tenths quicker than world record pace at 50 metres, turning in 23.76, before coming home in 48.88.
That was just two-hundredths of a second inside the mark set by Kliment Kolesnikov in St Petersburg last December.
Fastest qualifier Mitch Larkin was inside world record pace at halfway, and the Australian took second place in 49.54.