Tour money leader Hiroyuki Fujita was three strokes off the pace set by the South Korean duo of Hwang Jung Gon and S.K. Ho at the Casio World Open after the first round of play on Thursday.
Hwang had five birdies and finished with an eagle on No. 18 for a 7-under-par 65, that Ho later matched with his eighth birdie of the day on the same hole.
Masamichi Uehira, Kenichi Kuboya, Kunihiro Kamii and Makoto Inoue each fired in five birdies without a bogey for a first-round 67 at the par-72 Kochi Kuroshio Country Club in Kochi Prefecture to share third, while Fujita was among six golfers at 4-under-par 68.
Ryo Ishikawa, in the hunt for his second win on tour after a two-year victory drought, shot a 3-under-par 69 for a share of 13th place. Defending champion Tadahiro Takayama has withdrawn from the 200 million yen event due to a fever.
Sunday's winner will earn 40 million yen.