Defending champion Naomi Osaka claimed a straight-set victory at the US Open on her first Grand Slam appearance since withdrawing from the French Open.

The Japanese third seed, 23, ground down Czech world number 87 Marie Bouzkova for a 6-4 6-1 first-round win.

She will play world number 145 Olga Danilovic of Serbia next.

Osaka withdrew from Roland Garros in May, revealing she had "suffered long bouts of depression" since winning her first major title at the 2018 US Open.

The four-time major champion decided not to play at Wimbledon in June but returned for the Tokyo Olympics, where she lost in the third round.