Home favourite Kei Nishikori made a winning return to the ATP Tour's Japan Open with a straight sets win over compatriot Yuichi Sugita.
Third-seeded Nishikori, a recent semi-finalist at the US Open, continued his momentum on Monday as he dispatched Sugita 6-4 6-1 in just 82 minutes.
The two-time Japan Open champion will next face Frenchman Benoit Paire, who beat Nicolas Jarry 6-4 7-6 (7-1).
Canadian sixth seed Milos Raonic advanced in Tokyo with a typically powerful 6-3 6-4 win over Adrian Mannarino.
Fellow seeds Chung Hyeon and Diego Schwartzman both bowed out.
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Seventh-seeded Chung was beaten 6-3 3-6 6-2 by Canadian teenager Denis Shapovalov while Argentine Schwartzman, the fourth seed, fell 6-4 6-4 to Russian qualifier Daniil Medvedev.
Qualifiers Martin Klizan and Yosuke Watanuki progressed to the second round with wins over Steve Johnson and Robin Haase respectively.
