- Tag results for Japan Open
Nishikori faces qualifier Daniil Medvedev in Sunday's Tokyo final after the beanpole Russian overpowered Canada's Denis Shapovalov 6-3, 6-3.
Hsieh Su-Wei had too much experience on the big points as she dashed her teenage opponent's hopes of claiming a maiden WTA title in Hiroshima.
Carolina Marin returned to the court at the Japan Open one month after being crowned world champion for the third time in her career.
Kento Momota sank to his knees after a towering smash completed a comfortable win, kissing the Japanese badge on his shirt.
Kidambi Srikanth crashed out of the men's singles event after losing a marathon three-game quarterfinal to draw curtains on India's campaign at the Japan Open badminton tournament.
Sindhu was beaten by China's Gao Fangjie in the women's singles second round, her first preliminary exit in almost a year.
The Indian pair will face China's He Jiting and Tan Qiang next in the BWF World Tour Super 750 tournament.
In men's singles, HS Prannoy defeated current Asian Games gold medallist Jonathan Christie 21-18 21-17.
The victory did not come easy for PV Sindhu as she battled hard right from the opening game to earn points.
Sindhu has been outstanding this season with silver medals in all the major events this year -- the Commonwealth Games, the World Championship and the Asian Games.
Playing local favourite Okuhara for the third consecutive time, Sindhu could not bring to the fore her best game and committed too many errors
Parupalli Kashyap lost to Ya Igarashi 11-21, 21-18, 14-21 in an hour and five minutes in the second qualifying match.
The 23-year-old Zarina Diyas needed 77 minutes to win the battle of qualifiers in the tournament's championship match.
Sindhu, who had defeated Minatsu Mitani last week, will once again take on the Japanese in the opening round this week.