Japan came from behind to stun Germany 2-1 in their World Cup opener on Wednesday.
Second-half goals from Ritsu Doan and Takuma Asano helped Japan secure a big win in the Group E opener.
Doan smashed home from close range in the 75th minute, with Asano producing a moment of magic to put his team in front.
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He controlled a long ball then fended off Nico Schlotterbeck before scoring from a tight angle.
Both Japanese goal-scorers ply their trade in Germany's Bundesliga, with Doan at Freiburg and Asano at Bochum.
Manchester City's Ilkay Gundogan had put his side in the lead after converting a penalty in the 33rd minute.
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It comes just a day after minnows Saudi Arabia shocked Lionel Messi's Argentina.
They beat one of the World Cup favourites 2-1 and, just like Japan, came from behind to win their Group C clash.
Germany, who crashed out of the 2018 World Cup at the group stage round, face an uphill battle to qualify to the knockout stage, having suffered a shock defeat in the opening match of their campaign.
Speaking after the game, Thomas Muller said: "I feel we played well over long stretches, but in football you have to convert the superiority into goals. The efficiency wasn't there. It's ridiculous to start with a defeat.
"But when you see the way we conceded goals, you can say it wasn't an underserved loss."
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He added: "We have to process this now. Accepting defeat is never easy. But we have to remain objective - the defeat is easy to analyze in football terms, but difficult to grasp emotionally. If you're not efficient in football, you won't win anything."
Germany return to action on Sunday when they face Spain before taking on Costa Rica next Thursday.
Japan, meanwhile, resume their Qatar venture against Costa Rica on Sunday.
Topics: Football, Germany, Japan, Football World Cup
Nasir Jabbar