Tetsuji Hiratsuka shot a 4-under 66 on Friday to take a one-stroke lead over Takao Nogami at the halfway point of the Chunichi Crowns.
Hiratsuka, who last won at the 2007 Mitsubishi Diamond Cup for his fourth career title, carded five birdies and a bogey on the par-70 Nagoya Golf Club Wago Course for a 7-under 133 total.
Nogami shot a second-round 69 to finish where he started the day, one stroke off the lead.
Kenichi Kuboya and Naoya Sugiyama had 67s to join overnight leader Hiroyuki Fujita (71) in a share of third at 5-under.
Shingo Katayama (69), winner here in 2004 and 2006, was among six players a further shot behind.
Ryo Ishikawa dropped from fourth to a tie for 31st after struggling to a 74, while legendary 71-year-old Teruo Sugihara missed the cut after rounds of 84-87 in his 50th consecutive appearance at the Crowns.