Japan head coach Eddie Jones admitted Scotland were just too good for his side as they failed to repeat their World Cup giant-killing act.
The Brave Blossoms lit up the tournament on Saturday as they stunned South Africa in Brighton.
But two games in the space of five days proved a step too far for the Japanese as the Scots made the most of their tiring legs to run in five second-half tries and claimed a vital bonus point with their 45-10 success in Gloucester.
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However, Japan performed with enough verve and style in the first half to briefly take the lead through Amanaki Mafi's opening touchdown - leaving the Dark Blues fearing they were about to suffer the same humiliation dished out to the Springboks.
Jones said: "At half-time I thought we had a realistic chance of winning the game. They got into our 22 and they scored at least two tries off our turnovers. When we got into their 22, we were not clinical enough.
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"I thought they played really well. They were too good for us."
Ahead of the match, Jones promised his side would run Scotland "off their feet".
But there was no evidence of that as Mark Bennett grabbed a double on top of scores from John Hardie, Tommy Seymour and Finn Russell in a devastating 40-minute show.
"We are a fit team. We didn't run them in the second half, but I thought we did pretty well. We were just not good enough mate," was how Jones responded after being asked to reassess his earlier statement.
South Africa could hardly believe how competitive Japan were at the set-piece last Saturday and Scotland found it was no fluke either as their opponents gave them the run around for most of the opening period.
But skipper Greig Laidlaw saw the tide turn just before half-time when Seymour was only kept out by a last-gasp Ayumu Goromaru tackle.
The Gloucester scrum-half, who kicked 20 points on his return to Kingsholm, said: "I felt like we had them at half-time. They were starting to blow while we were starting to hold onto the ball and put them under some pressure.
"The clear message from Vern (Cotter) and the coaches at the break was, 'Don't panic. Just hold the ball'.
"We felt we had them fitness-wise. I believe this Scotland side is the fittest for a long, long time, and we showed that by playing for 80 minutes."
Scotland now top Pool B with a one-point lead over Japan.
But Laidlaw admitted their opponents' famous Springboks slaying had given them the jolt they needed ahead of their first fixture.
"Looking back [Japan's win over South Africa] probably actually helped our performance if I'm being honest," he said. "We were nervous at the start. To sit back and almost play last in the tournament was hard.
"But there was absolutely no place for complacency in our squad."
Scotland head coach Vern Cotter was pleased to see his side overcome their pre-match jitters but admitted he was concerned by their inability to shake off Japan during a first half that only saw them register four Laidlaw kicks.
He said: "There was constant pressure on the game. There will be things we will look at to ensure teams don't come back at us once we score. We'd like to make those points stick."
Top spot a possibility
The Scots will now have to prove they can deal with the four-day turnaround better than Japan as they prepare for Sunday's clash with the United States in Leeds.
But having avoided a potentially dangerous banana skin, hopes have been raised that they can now go on to challenge the Boks for top spot in their group.
The brutally honest Jones, though, does not give them much chance.
"South Africa will rebound," he insisted. "I will be really surprised if they don't put Fourie du Preez as the starting nine and let him run the game. If they do that, Scotland will find it difficult to beat them as I don't think they will get enough set-piece ball."
As for his side's own quarter-final ambitions, he said: "It comes down to Samoa in 10 days. If we can knock Samoa off, we have a fantastic chance. If we don't we have no chance. We hope the South Africa-Samoa match is like a UFC fight.
"Samoa has to back up seven days against us. What comes around goes around."
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