Kei Nishikori thrilled his home public while Marin Cilic held on to knockout the 2015 finalist as the Japan Open got underway under the closed roof of the Ariake Colosseum on a rainy Monday.
Top seed and two-time champion Nishikori, whose Sunday training session was watched by 8,000 eager spectators, advanced to the second round over Donald Young 4-6, 6-2, 6-2 as the American substituted ill Spaniard Nicolas Almagro.
Nishikori needed almost two hours to escape with the win, breaking fie time while losing his own serve once.
Asia's best player was competing for the first time in almost a month when he fell at the US Open to eventual champion Stan Wawrinka in the semi-finals two days after upsetting World number two Andy Murray.
Fourth seed Cilic, who led Croatia into next month's Davis Cup final at home against Argentina, knocked out 2015 runner-up Benoit Paire of France 6-0, 4-6, 6-3.
The Croatian won the first seven games of the match and only allowed Pair on the scoreboard after nearly half an hour of play.
But the heavily bearded Pair made a match of it, before going down under a barrage of a dozen Cilic aces.
"I was returning well in the first set, but he started playing better in the second set. Before the match I knew that he would be dangerous even if I went up in the score," Cilic said.
"I was missing too many balls and not making him play in the critical situations. In the third set I went back to basics. In the second set I didn't serve to well, so I tried to get my first serve percentage up."
Cilic reached the quarter-finals in Tokyo last season, losing to Nishikori. He next faces Fernando Verdasco, a winner over Go Soeda 6-7 (2-7), 6-3, 6-3. The Japanese qualifier now stands a dismal 0-10 lifetime at the home event.
Portugal's Joao Sousa reached the second round over Slovak Martin Klizan 4-6, 6-3, 6-3.