The four-time Asian champions will take on Brazil and Neymar at Tokyo’s Olympic stadium on Monday with the aim of beating the South Americans for the first time in a full international.
Hajime Moriyasu’s side are keen to test their mettle ahead of this winter’s World Cup, having been drawn in a tough group in Qatar with European heavyweights Germany and Spain.
“We are facing Brazil next and they play at a high level,” said striker Takuma Asano, who opened the scoring against Paraguay with a clinical finish.
“We need to see what we’re capable of doing against them and we just have to throw everything at them and try to keep that going.”
Underlining the scale of the task for the Brazil friendly, the South Americans thrashed South Korea 5-1 on Thursday in Seoul with Neymar scoring twice.
Moriyasu gave several fringe players a run-out against Paraguay, who won’t be in Qatar, after largely sticking to a tried-and-trusted line-up during World Cup qualifying.
“Everyone worked hard and created chances. It’s disappointing that we conceded, but we didn’t give much away at the back and we scored goals,” said the manager.
“I think we showed the gap between a team that will be at the World Cup and one that won’t.”
Bochum striker Asano gave Japan the lead when he chipped goalkeeper Santiago Rojas in the 36th minute after a perfectly weighted through-ball from Genki Haraguchi.
Daichi Kamada, who won the Europa League with Eintracht Frankfurt last month, doubled their lead in the 42nd minute with a header from Ritsu Doan’s cross.
Paraguay pulled one back 14 minutes into the second half through Derlis Gonzalez but Japan struck back immediately when Kaoru Mitoma, whose two goals against Australia in March clinched their place in Qatar, lifted the ball over Rojas from close range.
Rojas saved a penalty from Doan in the 70th minute but substitute Ao Tanaka bagged Japan’s fourth 15 minutes later.
After Brazil, Japan will play two games at home this month in a four-team friendly tournament also featuring Ghana, Chile and Tunisia.