Starting at 12 noon
Karolina PLISKOVA (CZE)  v Donna VEKIC (CRO)
Not before 1pm
Camila GIORGI (ITA) v Naomi OSAKA (JPN) 
Not before 4pm
Andrea SESTINI HLAVACKOVA (CZE) / Barbora STRYCOVA (CZE)  v Miyu KATO (JPN) / Makoto NINOMIYA (JPN)
Karolina Pliskova will play her first semifinal since losing to Petra Kvitova on the clay of Madrid in April. This is also the first time she reached this stage in Tokyo.
With 10 career titles to her credit, the Czech has twice as much winning experience than the remainder of the field combined.
Vekic had never reached the quarterfinal of a Premier event previously and now finds herself in the final four for the first time.
The 22-year-old has a formidable 6-1 winning record in semifinals during her career.
Pliskova won the last meeting of the pair back in 2014, when she came through in three sets in Monterrey. However, Vekic took the US Open match between the players in 2012.
Camila Giorgi will play US Open champion Naomi Osaka for the first time. The Italian has already scored a career-best victory over WTA World No.2 Caroline Wozniacki this week.
Osaka, the youngest player in the starting field at 20, is a previous runner-up in Tokyo, having reached the final as a wildcard in 2016.
Giorgi, meanwhile, has broken new ground by making the final four. Indeed, she had never previously won a set in her two previous visits to Tokyo.