Nick Kyrgios fired 14 aces as he brushed Ryan Harrison aside to reach the second round of the Japan Open on Tuesday.

Kyrgios triumphed 7-5 6-2 in 76 minutes, with his American opponent having no answer to the power of the Australian's serve.

"My serve is obviously a big weapon," said Kyrgios. "It gets me out of trouble when I'm not feeling so great and it's always a part of my game that I can rely on to win matches.

"I just think that I can't miss the same serve twice, so why not go after it on the second serve [too]?"

Kyrgios will now meet veteran Radek Stepanek, who saw off Stephane Robert 6-2 6-1, while seeded duo Gael Monfils and David Goffin prevailed against two home hopes.

Second seed Monfils wasted little time in beating Yuichi Sugita 6-3 6-1, and fifth seed Goffin claimed a 7-5 6-2 win against Yoshihito Nishioka.

Ivo Karlovic is into the next round following his win over Federico Delbonis, while there were also victories for Jiri Vesely, Juan Monaco, Gilles Simon, Marcos Baghdatis and Janko Tipsarevic.

Eighth seed Feliciano Lopez retired from his first-round match against James Duckworth at 4-2 down in the deciding set.