Defending champion Darren Clarke shot a 6-under-par 66 to share the lead with Hideki Kase and Christian Pena after the first round of the Mitsui Sumitomo VISA Taiheiyo Masters on Thursday.
Clarke, making his first appearance on the Japanese Tour this year, started on the 10th tee and birdied four of his first five holes in a round that featured seven birdies and a bogey on the Taiheiyo Club's Gotemba Course.
Clarke has won two titles in Japan; the 2001 Chunichi Crowns and last year's Mitsui Sumitomo VISA Taiheiyo Masters. Kase, a four-time winner on the Tour, joined the Northern Ireland player at the top of the leaderboard after matching his lowest round of the year with an eagle, five birdies and a bogey.
Pena eagled the par-5 18th to move into a tie for first place. Koki Idoki is alone in second after a 67. Five players are another stroke back.