Striker Shinji Okazaki scored two clinical first-half goals to spark Japan to a 5-1 home win over Finland in a World Cup qualifying warm-up on Wednesday.
The ease of the victory should give Japan a timely boost a week before the visit of Australia, who top their group in the final round of Asian 2010 qualifiers.
"We can't get carried away," Japan coach Takeshi Okada told reporters. "Australia are a completely different proposition. We will need to be at our best to beat them."
Okazaki fired Japan in front on 15 minutes with a fierce left-foot volley after springing Finland's offside trap.
Finland midfielder Tim Sparv smashed a long-range shot against the bar before Okazaki broke clear again, this time finishing with a low right-foot drive.
Shinji Kagawa stabbed home Japan's third on the stroke of halftime under the gaze of Australia coach Pim Verbeek, sitting alone on a cold evening at Tokyo's National Stadium.
Roni Porokara snatched a goal back for Finland moments after the break before Japan captain Yuji Nakazawa headed in his side's fourth and substitute Michihiru Yasuda completed the rout.
Finland were chosen as opponents for their size in preparation for Australia's aerial threat but the visitors were without several key first-team players.
Their 37-year-old captain Jari Litmanen, once of Barcelona and Liverpool, showed glimpses of his former magic but had little in the way of attacking support.
The Japanese were upset 1-0 by Bahrain in an Asian Cup qualifier last week, prompting Okada to criticise his players fiercely.
"We gave away another goal from a set piece so we clearly need to tighten up there still," said Okada before next week's clash in Yokohama. "Australia will punish us if we don't."
The teams have become fierce rivals since Australia beat Japan 3-1 at the 2006 World Cup in Germany. Japan gained revenge by knocking the Socceroos out of the Asian Cup in 2007.
Australia lead Group One in the final round of Asian World Cup qualifying with a perfect nine points from three games, two ahead of second-placed Japan.
The top two from each of the two five-team groups will qualify from Asia for the 2010 World Cup finals in South Africa.