Ishikawa, a quiet young man also known in Japan as Hanikami Oji, which means Bashful Prince, showed nothing resembling reluctance on another hot, humid day at Firestone Golf Club. He seized the moment with six birdies and no bogeys for a round of six-under-par 64 that tied him at 11 under with the 22-year-old Australian Jason Day (66) and put him a stroke behind the leader, Adam Scott (66), also of Australia.

This was Ishikawa’s lowest score in the 21 events he has played on American soil since coming to the United States in 2009 to test his game against the best players on the PGA Tour, the richest in the world. Although his on-course success has yet to approach the levels it has in Japan, where he has won 11 times and shot a round of 58, he has impressed in other ways — like announcing the donation of all his on-course earnings for this season, as well as $1,200 per birdie for the year, to Japanese earthquake and tsunami relief efforts.

The amount he has donated is approaching $1 million, which would more than double should he win the $1.4 million first-place check Sunday. That is something he says he is not allowing himself to consider.

“I think it’s a little too early to think about winning this whole thing as of now,” Ishikawa said through an interpreter. “But I do feel that I was able to play at a pretty good level, pretty high level today. Actually, I am a little bit surprised of how I performed out there.”

Scott, who at 31 is the old man at the top of the board, says he is not surprised. He first saw Ishikawa play in Japan four years ago and said he knew time was all that the teenager needed to become a major player on the world stage.

“I mean, this kid is really amazing,” Scott said. “Like I said, I think this week is really big for him. It’s great that he’s playing well over here probably for the first time. You know, his game is progressing really nicely, it seems.

“He’s got a very mature game, too. But as he grows and gets stronger and smarter about how to play the game, he could be a world-beater, or he already kind of is.”

As impressed as he is with Ishikawa’s game, Scott says he is struck even more by his social awareness and the gesture he has made by donating his earnings for the year.

“That’s an incredibly generous gesture from a young man, really,” Scott said. “And it’s nice to see. I think it probably inspires a lot of other people to give generously, too, so that’s the point of giving, I guess. It might have little impact in the big scheme of things in Japan, but it’s a huge impact worldwide, and hopefully, that helps the recovery and the rebuild.”

Ishikawa’s enormous popularity in Japan comes as close as anyone’s has to what Tiger Woods’s was two years ago in the United States. It is not difficult to see the root of Ishikawa’s appeal in the earnest way he answers questions, the self-effacing responses he gives, his movie-star good looks and his bearing, which on the golf course can border on regal.

Last week, he trimmed the flowing dark hair that cascaded from beneath his caps and visors. When he ran into Woods on the putting green this week, Woods was just the latest person to ask him why. Ishikawa smiled and told Woods: “Too hot here. Too hot.”

Ishikawa was hot from the start Saturday, sinking a 30-footer for birdie at No. 1, chipping in from 25 feet at No. 4 after just missing an 8-foot birdie putt at No. 3 and then stuffing a short iron to inside 3 feet for tap-in birdie at the sixth hole. He missed the green and got up and down for par at Nos. 8 and 9 and started the back with a birdie at No. 10 from 8 feet. He made a 14-foot putt from off the green at the par-3 12th, and hit a wedge to 4 feet to help birdie the 17th.

Like many star athletes from Japan in the United States, Ishikawa is followed by a large news media contingent from his home country. Unlike some, though, he does not hide from reporters but embraces the opportunity. On Saturday, he sat comfortably in a canvas chair provided by one of the 20 journalists who encircled him outside the media center and patiently answered question after question.

Whether he wins or not, Ishikawa will gain some valuable experience Sunday. He will play in the final pairing with Scott, right behind Day and the surprising rookie Keegan Bradley, who is tied for fourth at 10 under. Perhaps Ishikawa would have been better off in the next-to-last pairing, on the fringe of fame’s unrelenting stare. On the other hand, Ishikawa has dealt with this dream for more than five years. His attitude is refreshing.

“I feel that I’m able to go out there and give what I have, give my 100 percent,” he said.

And if that is not good enough, there is always the next time, something that is as close to a sure thing as anything in golf these days.