Defending champion Andy Murray blew out the cobwebs with a 7-6, 6-4 win over towering Croat Ivo Karlovic on Tuesday in his first match since winning last month's U.S. Open.
The Olympic gold medallist had been scheduled to face Gael Monfils in the first round of the $1.28 million hardcourt event but the Frenchman pulled out with a knee injury.
Japan's Kei Nishikori survived a fright against countryman Go Soeda, the eighth seed squeaking through 4-6, 6-2, 6-3 to the relief of Tokyo organisers in two hours, 29 minutes.
Murray got a workout from 2.08 metres Karlovic and was forced into a tiebreak in the first set which the Scot took 9-7 with a superb running forehand pass down the line.
A quick change of wardrobe and Murray, now in all black, waited for his moment in the second as Karlovic slammed down 18 aces, converting his third match point with a vicious backhand to the Croatian's body after one hour, 38 minutes.
Nishikori, who reached his first semi-final of the year in Kuala Lumpur last week, next plays Spaniard Tommy Robredo, a 6-2, 6-4 winner over Finland's Jarkko Nieminen.
Big serving Milos Raonic hit 10 aces in a 6-4, 6-4 victory over Czech Radek Stepanek, sending the Canadian through to face Serbia's Viktor Troicki.