Nishikori won 84 per cent of first-serve points in front of a home crowd and did not face a break point in the 90-minute win over his eighth-seeded opponent.
Nishikori, who has not won an ATP World Tour title since Memphis in 2016, will face Daniil Medvedev in Sunday's final.
Medvedev became the first qualifier to make the final in Tokyo in 16 years by beating Denis Shapovalov 6-3, 6-3.
The Russian saved the only break point he faced, and has now held serve in 36 of 40 service games this week.
Nishikori, who has won this tournament twice, beat Medvedev in their only previous meeting in Monte Carlo earlier this year on his way to the final.
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