Japan humiliated Euro 2024 hosts Germany 4-1 in a friendly international on Saturday, piling the pressure on struggling coach Hansi Flick who defiantly insisted he remains the right man for the job.
Japan, who also contributed to Germany's group stage exit at the World Cup with a 2-1 win in Qatar last year, scored twice in each half.
The defeat raises more questions over Flick's future, nine months out from Germany hosting the European Championships.
A "brutally disappointed" Flick refused to back down after the game.
"I think we're doing well -- and I'm the right manager. But I know things can change in professional football and I can't see what's to come," he said.
Germany captain Ilkay Gundogan said simply "we are not good enough right now, it's a completely bitter day -- we all need to ask questions of ourselves."
Junya Ito and Ayase Ueda scored either side of a Leroy Sane strike in the first half, Japan taking a 2-1 lead into halftime as the home fans jeered the home side.
Germany continued their limp performance in the second half, with Japan scoring twice in the final five minutes through Takuma Asano and Ao Tanaka, to seal a dominant performance.
Japan manager Hajime Moriyasu said his side "actually had many more chances to score" but "the main thing is that we won."
"To win a game here in Germany, in this difficult situation, we have done well."
- Boos and whistles -
Flick promised before the game Germany would "play our core team", pledging to shelve an experimental approach which saw his side win just one of five games since their disastrous World Cup exit.
Flick however started Nico Schlotterbeck at left-back, a position the Borussia Dortmund centre-back has played only twice in his senior career, both times off the bench.
Schlotterbeck's inexperience in the position showed, the defender losing Japan winger Yukinari Sugawara after 11 minutes and allowing the winger to cross for Ito to score the opener.
Germany equalised shortly after, freshly minted captain Ilkay Gundogan finding Florian Wirtz on the edge of the box.
The playmaker, who has shone in Xabi Alonso's table-topping Bayer Leverkusen midfield this season, shaped to shoot but instead laid off a pass for Sane, who calmly slotted home.
The superbly worked goal hinted at a Germany comeback but Japan would strike next, Sugawara again finding space down Schlotterbeck's right flank.
The AZ Alkmaar winger found Ito, who threaded a pass through the flat-footed Germany defence, allowing Ueda to score.
The home fans' silence turned to boos and whistles at the break, which continued into the second half as Germany dominated possession but failed to break down a dogged Japanese defence.
With Germany chasing an equaliser, Japan scored twice late, first through Asano -- who scored the winner in Qatar -- and then from Tanaka in injury time to round out a stunning and dominant performance.
Despite a historical reluctance to sack managers, particularly so close to a major tournament, Germany may be forced to part with tradition, particularly with former Bayern boss Julian Nagelsmann seemingly waiting in the wings.
Up next for Germany is Tuesday's meeting with France in Dortmund, a team which will be delighted to capitalise on the space afforded by the German defence.
A third win in a row continued Japan's strong preparation for January's Asia Cup in Qatar, a competition they have won a record four times.