The World number one beat Croatian Donna Vekic 6-3 4-6 7-6 (7-4) at the Porsche Tennis Grand Prix.
Osaka will now face Anett Kontaveit, who was able to progress after Victoria Azarenka retired.
Petra Kvitova will face Kiki Bertens in the other semi-final.
Ruthless Man City thump Newcastle to reach League Cup final
Omar Marmoush scored twice as Manchester City set up a League Cup final date with Arsenal after a comprehensive 3-1 second-leg victory over visiting Newcastle United secured a 5-1 aggregate win in their semi-final on Wednesday.
Alexandra Eala stages comeback to reach Mubadala quarter-finals
Filipina teenager Alexandra Eala fought back from the brink of defeat to reach the quarter-finals of the Mubadala Abu Dhabi Open after a marathon win over Aliaksandra Sasnovich.
F1 legend Mika Häkkinen turns brand ambassador for Only Legends Drive UAE
Two-time Formula One World Champion Mika Häkkinen will step in as the brand ambassador of the ultra-luxury four-day supercar rally - Only Legends Drive UAE, that kicks off on March 19.
Guardiola vows to speak up for victims of global conflicts
Pep Guardiola said he will continue to use his platform as Manchester City manager to speak up for victims of global conflicts and violence.
Arsenal beat Chelsea 1-0 to reach League Cup final
Arsenal booked their spot in the League Cup final by beating Chelsea 1-0 at the Emirates Stadium on Tuesday thanks to an injury-time goal by former Blues attacker Kai Havertz, sealing an aggregate 4-2 win over their London rivals.
