Ryo Ishikawa left himself with an eight-shot deficit to make up in the final round after only managing a 1-under 69 on Saturday at the season-ending Nippon Series JT Cup.
In ideal conditions for low scoring, the 19-year-old phenom dropped from a share of sixth into a tie for 10th at 3-under 207 at Tokyo Yomiuri Country Club.
Overnight leader Yuta Ikeda, the only other player with a chance to pass money leader Kim Kyung Tae, had a 71 to fall four strokes off the pace.
Veteran Hiroyuki Fujita turned in the day's low of 64 for an 11-under 199 total and a three-shot lead over Australian Brendan Jones.