Shinji Kagawa also found the target shortly before the break while Yuji Nakazawa and substitute full-back Michihiro Yasuda scored in the second half to round off the emphatic win.

With midfielder Yasuhito Endo and defender Marcus Tulio Tanaka back in service after having missed the previous two matches in January due to injury, Japan looked strong throughout.

The hosts attacked from the start and Okazaki put them ahead in the 15th minute after latching onto a long ball from Atsuto Uchida.

Finland came close to equalising in the 26th minute when Tim Sparv hit the bar but Japan added a second goal in the 32nd minute when the Shimizu S-Pulse forward Okazaki blasted home a Kengo Nakamura lob from the edge of the box.

Just before the break Kagawa intercepted a Finland pass firing home to put Japan in a strong position at half-time.

Finland reduced the deficit five minutes after the break when Japan goalkeeper Ryota Tsuzuki punched a Jari Litmanen corner away but midfielder Roni Porokara reacted well to score from close range.

But Japan made it 4-1 with a header from Nakazawa in the 57th minute before Gamba Osaka full-back Yasuda, who came off the bench in the 81st minute, completed the scoring shortly before the final whistle when he cut inside before firing home from the edge of the box.

"I'm happy with our performance but there were some aspects that I'm not happy about," Japan coach Takeshi Okada said.

"When we play Australia, we need to play better or we will be in trouble.

"I know Australia were watching the game and will work on what they've learned from today. It won't be easy for us."

"However, some of our players have done more than I expected and that's certainly a positive thing for us."

Finland coach Stuart Baxter, meanwhile, found positives to take from the defeat.

"The Japanese team played very well and their movement and passing were very good," he said.

"I'm disappointed that we gave away such easy goals but on the other hand, I'm pleased with the performance from our younger players. Tim Sparv and Roni Porokara were very good and Teemu Pukki looked dangerous when he came on.

"It has been a great experience for them and in the long term it will be very good for the Finish football."

Japan play Australia in a World Cup qualifier next Wednesday in Yokohama while Finland will play Portugal in another warm-up before their World Cup qualifier with Wales on March 28.