Okazaki opened the scoring after receiving a long pass from Atsuto Uchida in the 15th minute, and then he made it two on another long pass from Kengo Nakamura in the 32nd minute.
Shortly before the break, midfielder Shinji Kagawa dribbled through to beat three defenders and score past goalkeeper Tomi Maanoja for the third goal.
However, the Japanese regained the initiative and added another when defender Yuji Nakazawa jumped highest on a Uchida cross seven minutes later. Substitute Michihiro Yasuda completed the scoring in the 86th minute.
"I'm just glad that I was able to score. I was able to get past defenders in the first half very well, but my performance was not good enough in the second half," said Okazaki. "I want to keep the momentum to beat Australia next week."
"First of all, we must eliminate their chances off set-piece plays. Hopefully, we can play our best football next week," he added.