Just like they did in their opener against the Germans, Japan produced a stirring fightback at Khalifa International Stadium on Thursday night to come from behind at halftime against one of the competition's former champions and perennial contenders to claim a 2-1 victory -- courtesy of quickfire goals after the break from Ritsu Doan and Ao Tanaka.
The result meant that the Samurai Blue's shocking 1-0 loss to Costa Rica four days earlier ultimately mattered little in their quest to reach the knockout round, but was also all the more puzzling given how poorly they had played in that tie yet managed to defeat both Germany and Spain.
Next up for the Japanese is a last-16 tie on Monday against 2018 runners-up Croatia, which is a match that they will likely head into as underdogs once more.
But considering the upsets they have already pulled off in the group stage alone, it is understandable why Japan will hold no fear for anyone they come up against.
"We have the possibility to beat every team," forward Takuma Asano, who scored the winner against Germany, told ESPN exclusively in the immediate aftermath of Thursday's triumph over Spain.
"We just need to play at 100% and give our everything for every game. We only need to think about that.
"I feel very happy (to beat Spain) but we already have to prepare for the next game (against Croatia) from this very moment. We have to focus on that now and just do everything we can for that, as we do every time."
Asano did however acknowledge the fact that they were beaten by Costa Rica further emphasises how nothing can be taken for certain at the World Cup.
"Everyone of our team always plays at 100% but, as you know, everything is possible in football, right?" he added.
"That's why there is always the possibility that we win or lose. The only thing we can control is that we give 100% for every game, even before we know if it's going to be a win or loss."
Another member of the Samurai Blue team that was beaming with pride on Thursday was winger Takefusa Kubo -- currently on the books of LaLiga outfit Real Sociedad and one who has spent almost his entire career in Spain.
"Thinking does not cost anything. The good thing about this team is that we only think game by game," said Kubo, when asked if Japan believed they could keep upsetting more-illustrious opponents.
"We're not as formidable as Spain or Brazil where we can think even further about subsequent rounds. We have to focus on Croatia.
Considering the pre-tournament target for Japan was to reach the quarterfinals for the first time ever, Kubo also believes Monday could be an even more memorable outing than their recent victories in the past fortnight over two teams that have combined for five World Cup crowns.
"Let's hope not," answered Kubo, replying to a query on whether beating Spain would go down as the biggest moment ever in Japanese football.
"Let's hope it's against Croatia. Let's see if we can win and continue to pass into the next rounds.
"(A win over Croatia) would be the night that can change the history (of Japanese football)."