Japan have flown in under the radar to become the team to beat, along with England, at the Women's World Cup and boasting the tournament's leading scorer in Hinata Miyazawa.

The United States, the holders, and a European contingent led by continental champions England were touted as title contenders going into the World Cup.

Nobody was talking about Futoshi Ikeda's Japan, who are ranked 11th in the world by Fifa.

Even back home, expectations that they could pull off a repeat of their 2011 World Cup triumph were low.

"I think we were left behind by the sudden strides that the rest of the world were making," former Japan coach Asako Takakura, who led the team at the 2019 World Cup, told AFP ahead of the 2023 edition.

Japan went out in the last 16 in 2019 but are already into the quarterfinals four years later.

They won all three of their group games – a record matched only by Sweden and England – scoring 11 times and not conceding.

Wins over Costa Rica and Zambia were expected, but it was the 4-0 thrashing of Spain which made the rest of the tournament sit up and take notice.

They followed that up with a 3-1 victory over former champions Norway on Saturday and now face the United States or Sweden for a place in the semifinals.

"I think they showed maybe why they have been the best team so far today," Norway's Barcelona star Caroline Graham Hansen told reporters afterwards.

"They're so disciplined and very structured in the way they play offence and defence."

Sergio Echigo is a famously hard to please columnist for the Nikkan Sports newspaper in Japan. Even he is impressed.

"Japan haven't really looked in danger in these four games so far," he wrote, saying that Norway played "old-fashioned football" compared to Japan.

"They didn't have technique but they had power," he wrote.

"But this isn't an era when you can win just by using your power.

"Japan use passes, dummies, dribbles. They look greater than the sum of their parts."

- Starting to believe -

What is so striking about Japan is how devastating they are going forward and in front of goal.

Spain had much more of the ball but had only two shots on target.

Japan had eight attempts in total, got six on target and scored four.

Norway coach Hege Riise said Japan will be hard to beat.

"They are a great team with a lot of good players and tactics," she said.

"The combination of tiki-taka with direct play is hard to defend."

The 23-year-old Miyazawa, who plays in Japan's domestic league, has been especially clinical.

Combining speed with coolness in front of goal, she tops the scoring charts at the World Cup with five goals, despite never being prolific for Japan before.

"World, watch out for this one," former USA striker Jessica McDonald told Optus Sport.

"She's on a roll and once a striker starts scoring goals it's so hard to stop," McDonald said.

"Once you start gaining that momentum, once you start gaining that confidence in front of goal, you're scoring bangers in every game."

After low expectations at the start of the tournament in Australia and New Zealand, football fever is starting to reignite in Japan.

The team's deserved win over Norway was front-page news in two national newspapers on Sunday.

"Could we see a repeat of what happened 12 years ago?" wrote Echigo.

"I want to start believing."