The towering Croatian, runner-up to Roger Federer at this year's Wimbledon, took just 73 minutes to complete a one-sided victory in Tokyo against a player ranked 110 places below him.
World number five Cilic, a former US Open champion, rifled eight aces and totally dominated on serve on a speedy hardcourt surface that suits his power game.
South African Kevin Anderson, who was beaten by Rafa Nadal in the US Open final last month, also advanced in straight sets, the fifth seed ousting Frenchman Gilles Simon 6-2, 7-6.
In other matches, American Ryan Harrison overcame Japan's Yusuke Takahashi 6-4, 4-6, 6-4 while Frenchman Adrian Mannarino dumped out another local favourite, Go Soeda, 7-5, 7-6.