Japan manager Hajime Moriyasu hailed a win made in the Bundesliga after his Blue Samurai stunned four-time champions Germany 2-1 in their World Cup opener on Wednesday.

Eight of Japan's squad are based in Germany and it was two of those players who scored the goals that sealed a historic victory for the Asian side.

Freiburg's Ritsu Doan and Bochum's Takuma Asano both came off the bench to strike late in the second half and help Japan pull off an unlikely comeback against a German team leading through Ilkay Gundogan's first-half penalty.

Moriyasu said a second-half tactical switch had helped turn the tide but credited his players' footballing education in Europe as the real foundation for the win.

"We have seven players in the Bundesliga and one in the German second division, but we have many more playing in big leagues in Europe and that has played a big part in our development," he said.

"Germany are a big team but our players stayed calm and patient."

Japan looked unlikely to take anything from the match after a timid first half where Germany should have been more than a solitary goal ahead.

Goalkeeper Shuchi Gonda kept Japan in it with a string of good saves after the break, and when space began to open up in Germany's defense, Doan and Asano took advantage.

Gonda said that the team had been inspired by watching Saudi Arabia come from behind to sink Argentina the previous day.

"We knew that like Saudi Arabia if they didn't score any more goals and we kept going until the end, we would get our chances," he said.

"Even if I concede one, my job is to make sure I don't concede anymore and give us a chance of turning it around."

Doan and Asano both helped inject some pace and urgency into Japan as Moriyasu brought on a host of attacking options in the second half.

Doan lit the spark when he gobbled up a loose ball after German goalkeeper Manuel Neuer had parried it into his path in the 75th minute.

Asano completed a remarkable turnaround eight minutes later, outmuscling Nico Schlotterbeck and smashing the ball in at Neuer's near post.

"It was a team win. Before the game, we talked about how the players that started would give everything for an hour, and then we would come in and finish it off," said Doan.

"That's how it turned out and it was a fantastic day."

Japan next play Costa Rica before finishing their Group E campaign against Spain.

Moriyasu has set his team the goal of reaching at least the quarter-finals but he warned his players not to get carried away just yet.

"I want us to keep a level head after this and look at what we could have done better and look to win the next match," he said.