TOKYO, Nov 11, 2012 (AFP) - Ishikawa, who is now 21 years and one month old, fired a 4-under-par 68 for a winning total of 15-under 273 in the 150 million yen ($1.9 million) Taiheiyo Masters, sanctioned by the Japan Golf Tour (JGTO).
His last victory came at the same event in 2010.
"I had long lost the taste, or the feeling of victory, so I feel strange. I'm happy but don't really feel it," a tearful Ishikawa told reporters.
It was Ishikawa's 10th victory on the JGTO tour, which also makes him the youngest player to register the record.
Ishikawa entered the final round at the par-72 Taiheiyo Club in central Shizuoka prefecture with a one-stroke lead, the first time in over two years that he stood alone at the top of the leaderboard on the final day.
He was followed by Michio Matsumura in second and Yoshinori Fujimoto in third.
Ishikawa has been keenly sought by advertisers since May 2007 when he became the the youngest men's winner on a major tour by lifting the domestic Munsingwear Open KSB Cup aged 15 years and eight months. He turned professional in 2008.