Japan Open top seed Marin Cilic produced a dominant display to overcome Japan Open first-round opponent Stefano Tsitsipas.
The 2014 US Open champion eased to a 6-3 6-2 triumph against his 19-year-old opponent on Monday.
World number five Cilic - who lost this year's Wimbledon final to Roger Federer - will now face wildcard Yasutaka Uchiyama following the home hope's 6-3 3-6 6-1 victory over Franko Skugor.
Albert Ramos Vinolas, seeded seventh, suffered a surprise 6-2 2-6 6-3 loss to Jiri Vesely, while Kevin Anderson served up 17 aces as he overcame Gilles Simon 6-2 7-6 (8-6).
Next up for fifth seed Anderson is a meeting with American Ryan Harrison, a 6-4 4-6 6-4 winner against Yusuke Takahashi.
Elsewhere in the draw there were wins for Adrian Mannarino and Bernard Tomic, while Ivo Karlovic's match with Matthew Ebden stood at 1-1 in the first set when rain brought play to a halt.