Forrest carded nine birdies and one bogey in his second-round 62, finishing with back-to-back birdies to reach 10-under on Friday.

Herbert enjoyed nine birdies and two bogeys in his round of seven-under, while Thailand's Janewattananond finished with a hat-trick of birdies at the 16th, 17th and 18th to also sign for a 63.

Victorian Herbert, whose arrival into Japan was delayed by travel issues earlier in the week, sits 11th on the Race to Dubai Rankings and believes his late arrival may have been beneficial.

"It was a bit of a travel debacle getting here. It might have been a bit of a blessing in disguise," the 27-year-old said.

"You don't have the same memories from hitting bad shots in the practice round, or knowing where the bad places are. Just stand up, look at a target, and hit it.

"Nick, my caddie, got here when he should have and did all the work for me. That speaks a lot to why we are 10-under through 36 holes."

Compatriot Brad Kennedy followed up his opening 65 with a 72 to be in a tie for 46th at three-under in Omitama.

The highlight of Forrest's round came at the 8th – his penultimate hole – where he drained an enormous birdie putt, while another gain on the 9th earned the afternoon starter a share of the lead.

"It was a bit of a travel debacle getting here. It might have been a bit of a blessing in disguise. You don't have the same memories from hitting bad shots in the practice round ..." - Lucas Hebert.

"I didn't realise where I was until the last green and I thought 'oh this is for a 62'. I just plugged away all day," he said.

"I got the putter going. I didn't really hole any putts yesterday but managed to roll in a few, got one in on the eighth – our 17th – from a long way.

"I'm looking forward to the weekend. The course is firming up a bit. There have been some tucked pins and I imagine it will stay the same going into the weekend."

German Maximilian Kieffer was one stroke behind the co-leaders at nine-under, with England's Jordan Smith, home favourite Takumi Kanaya and South African Deon Germishuys all a further shot back.

Four-time major champion Ernie Els put on a show, holing his bunker shot for an eagle on the 16th to reach four-under and safely make the cut.