World No. 1 Yui Kamiji earned her third Grand Slam title of the season by winning the women's singles final at the U.S. Open wheelchair championships on Sunday.

The top-seeded Japanese beat the second-seeded Diede de Groot of the Netherlands 7-5, 6-2 in the 1-hour, 11-minute match at the Billie Jean King National Tennis Center to be crowned U.S. Open champion for the second time following her victory in 2014.

The 23-year-old Kamiji, who made a semifinal exit from Wimbledon in July which de Groot went on to win, also claimed the singles titles at the Australian Open in January and French Open in June.

"This is my first victory here since 2014 and I'm happy," said Kamiji, who won 73 percent of her second-serve return points, breaking her opponent's serve four times in the first set and three times in the second.

"I'm playing better now, strategically and mentally, but maybe I was more naive and happier with the win in 2014 when I played hard without thinking too much," she said.