The Japan Tennis Championships will have a new winner this year after Kei Nishikori was ousted by Benoit Paire in Tokyo.

Nishikori was expected to reach the decider but the defending champion was shocked 1-6 6-4 6-2 in front of his home crowd on Saturday.

Paire, who improved to 51-23 this year, overcame a slow start, eventually triumphing in less than two hours as the unseeded Frenchman set up a date with top seed Stan Wawrinka in the final on Sunday.

Nishikori stormed out of the blocks in the semi-final clash, breaking twice in a one-sided first set.

The two-time Tokyo winner threatened to run away with the match but Paire fended off five break points in the seventh game to remain 4-3 ahead, which proved decisive as the latter levelled the contest on Nishikori's serve.

Paire never looked back from that point as Nishikori faltered dramatically in the third, summed up in the final game after double-faulting and sending a shot long on match point.

Standing in Paire's way is Wawrinka, who accounted for Gilles Muller in straight sets.

Wawrinka advanced to his fourth final of the year via a 6-4 7-6 (7-5) win over the unseeded high-flyer from Luxembourg.

Muller had upstaged third seed Gilles Simon and fifth seed Kevin Anderson en route to the semi-finals, but the 2008 US Open quarter-finalist was no match for Wawrinka, who tallied his 47th win in 60 matches this season.

Wawrinka claimed the decisive break of serve for a 4-3 lead in the seventh game of the opening set and the Swiss star never looked back.

The second set was more evenly-contested, Muller dropping serve in the third game only to break back immediately at 2-2.

Wawrinka threatened to close out the match and although Muller managed to force a tie-break, that is where the latter came unstuck as he sent a backhand volley wide to bow out.