Rickie Fowler and Andrew Putnam share a one-stroke lead after the second round of the PGA's Zozo Championship, where scores were low with drier conditions after rain in the first round.
It was a tougher day for former Masters champion Hideki Matsuyama, who is also the defending champion and the hometown favourite.
He was 10 strokes off the pace after a 69, having opened with a 71 on Thursday.
Putnam had an eight-under 62 and Fowler was in at 63, putting both Americans at 10-under after two rounds at the Accordia Golf Narashino Country Club on the outskirts of Tokyo.
The low round with a 61 - and a course record - went to John Huh. The American was two strokes off the pace.
One stroke behind the leaders was Keegan Bradley, who shot a 65 on Friday.
Huh was asked if he had a round of 59 on his mind.
"Not really," he said. "I knew if I made a couple more birdies it would have been nice, but I really never thought about a 59 in my head."
Australia's Cam Davies is tied for 24th after shooting a three-under second-day 67.
The Zozo Championship is the only PGA Tour event in Japan with a purse of $US11 million.
