Hideki Matsuyama fired a round-of-the-day 65 to open up a three-shot advantage at the WGC-HSBC Champions, as Rory McIlroy made a move up the leaderboard.
Matsuyama mixed nine birdies with two bogeys on his way to setting the clubhouse target in Shanghai, while McIlroy heads in to the weekend six strokes off the pace after a much-improved round.
Resuming two strokes adrift of overnight pacesetter Rikard Karlberg, Matsuyama recovered from a first-hole blemish to birdie the next two and add two more from the seventh on his way to reaching the turn in 34.
The world No 10 opened his back-nine with a hat-trick of gains to move top of the leaderboard, before extending his advantage to three strokes by picking up shots at the par-five 14th and 18th.
"I'm really happy with how it ended up today," Matsuyama said. "During the warm-up this morning, it was starting to get windy and I thought maybe just a couple under par would be a good score.
"I have been playing well but today I hit some good second shots and made some putts and that's what made the round score well for me."
Defending champion Russell Knox, looking to become the only player other than Tiger Woods to successfully defend a WGC title, posted a four-under 68 to join American Bill Haas in joint-second.
Birdies over his final three holes lifted Francesco Molinari to within five strokes of the lead alongside Richard Bland and Daniel Berger, with McIlroy posting a six-under 66 to join the group a further shot back.
McIlroy reached the turn in 33 and added three gains in a four-hole stretch along the back nine, before bouncing back from finding the hazard and dropping a shot at the 16th to birdie the last.
The world No 3 is joined on seven under by Paul Casey, Ross Fisher and home favourite Xinjun Zhang, with Rickie Fowler seven off the pace after bogey three of his opening five holes.
Masters champion Danny Willett struggled to a six-over 78 and US Open winner Dustin Johnson posted a second successive 74, as Adam Scott fired a back-nine 42 on his way to a second-round 80.
Watch the WGC-HSBC Champions throughout the weekend live on Sky Sports 4 - your home of golf. Live coverage begins on Saturday from 4am.