Earlier, seventh seed Jelena Jankovic eased past France's Marion Bartoli 6-4, 6-3 to reach the last four of the $2 million tournament in Tokyo.
Sharapova, 25th in the world after shoulder surgery last October, kept the nervous event organisers happy after a glut of early exits by top-seeded players.
"I feel like its almost automatic again," the three-times grand slam winner said. "Figuring things out and being patient. It didn't come easy to me at first.
"The goal is to be aggressive no matter what the situation is. It's about execution and not making errors when you have to step up and win big points."
The Russian, still looking for her first title since her return from injury, rattled off four straight games to take the opening set.
Sharapova's big-match experience told again at the business end of the second when she broke her opponent's serve at 6-5 with a ferocious backhand to close out the quarter-final.
The 2005 Tokyo champion will face the winner of the match between 11th seed Agnieszka Radwanska of Poland and Slovakia's Magdalena Rybarikova in the semi-finals.
JANKOVIC SOLID
Jankovic, who finished 2008 at the top of the rankings, never looked in danger of following the top six seeds out of the event.
"It makes a big difference when my mind is on tennis," the Serb said after beating Bartoli for the first time in their last five meetings.
"I play at another level. So many things happened this year. My mum got sick and had surgery.
"Before my US Open second round defeat, my grandmother died and tennis became secondary. Other things were more important in life."
Jankovic completed victory over Bartoli by forcing the 14th seed to dump a backhand into the net, ending a point which neatly encapsulated their match.
A tournament which began with nine of the world's top 10 was left with just one after eighth seed Victoria Azarenka of Belarus was beaten by China's Li Na 7-6, 4-6, 7-6.
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