Naomi Osaka became the first Japanese to win a Grand Slam tennis singles title Sunday at the U.S. Open, sparking celebrations among her family and compatriots.

Osaka's 73-year-old grandfather Tetsuo told reporters at his home in Nemuro, Hokkaido, that he and his wife were ecstatic after watching their granddaughter's 6-2, 6-4 victory over multi-title winner Serena Williams on television.

He said Osaka had called them after the match to tell them about it, adding that he hopes her achievement will lift the spirits of local people still reeling from a recent powerful earthquake.

Prime Minister Shinzo Abe took to Instagram to praise Osaka's accomplishment. "At difficult times like now, thank you for the energy and inspiration," his message read.

Residents of her namesake city of Osaka, where she was born, also expressed their delight.

"I subscribed to satellite TV to see the game, and I got goose bumps when she won," said Yuta Yokoyama, 33, who was practicing at a tennis court.

Kazuki Nakadate, 26, said he had never expected a Japanese to win the tournament. "She showed a bullish attitude even toward a legend like Serena Williams," he said.

Ai Sato, 55, said, "We've had lots of gloomy news recently such as typhoons and earthquakes. But I think (her victory) will help encourage people living in the affected areas."

At the Tokyo head office of Nissin Foods Holdings Co., one of Osaka's sponsors, about 150 people watched the match on a large-screen television.

"She has inspired Japan at a time when the country is reeling in the aftermath of the Hokkaido quake and torrential rain in western Japan," said 35-year-old Shuichi Fukushima, whose voice had gone hoarse from cheering.

People in Haiti, the homeland of Osaka's father, also celebrated her win.

"We are proud of her," Mac Keven Frederic, 45, said. "With this victory, many young Haitian women will take up tennis."

Osaka's victory is an "honor" for Haitian people, as it proves that people from smaller countries can still triumph, said 63-year-old Hilario Batista Felix.

(Naomi Osaka's grandfather Tetsuo speaks to reporters in Nemuro, Hokkaido)