Japan have done it again, this time against the team ranked No 1 in the world two weeks ago. The World Cup hosts came from nine points down to win after playing with pace, skill and fervour that the humidity and time could not dim.

Such was the thunderous roar when the final whistle sounded it would have caused the nearby Mount Fuji to wobble. There were times when they looked like the All Blacks in red and white jerseys, offloading, evading tackles and breaking from deep to make one of the tightest defences in world rugby scramble with increasing desperation.

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Japan stunned the rugby world four years ago when they defeated South Africa in Brighton, and they are now on course to meet the Springboks in the last eight, but this was different. The 1995 and 2007 winners were on the way down, bloated and complacent, but Ireland did not throw this match away. They were in control after 20 minutes having scored two tries from kicks, but as soon as Michael Leitch, the hosts’ tournament captain, came off the bench before the half-hour, the game changed.

Japan had started with daring and adventure and should have gone ahead in the third minute when Kotaro Matsushima, who scored a hat-trick against Russia on the opening night, got in front of Jacob Stockdale as they chased a kick to Ireland’s line but then veered sideways, as if expecting an awkward bounce.

They were unfortunate when Josh van der Flier’s knock-on two metres from his line was not picked up, but they were becoming frustrated at their failure to reward pressure with points when Leitch came on to replace the injured Amanaki Mafi in the back row.

He quickly touched the ball three times, driving hard and straight each time, sucking in defenders, making a few metres, getting to the gainline and putting his side on the front foot. Japan had quicker ball to use and Ireland conceded penalties as they looked to slow down possession, Peter O’Mahony and Van der Flier presenting Yu Tamura with the opportunities to reduce Ireland’s interval lead to three points.

Facebook Twitter Pinterest Joy for Japan, but dejection for Ireland. Photograph: Anne-Christine Poujoulat/AFP/Getty Images

Leitch had been on the field a few minutes when, in the game’s seminal moment, Japan shoved Ireland off their ball in the scrum, won a penalty and galvanised a crowd who started to believe rather than hope.

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The question was whether Japan could sustain such pace and skill. The answer was a resounding yes. It was to Ireland’s credit that, although they became stretched and their defending became more frantic, they did not snap. Some of the home side’s play was so thrillingly inventive and skilfully executed that there was nothing tier two about them. They looked like a side that belonged at least in the quarter-finals and it would be sweet justice for them if they made it there at the expense of Scotland, who more than any other of the Six Nations ensured that World Rugby’s Nations League, which would have provided a pathway for emerging nations, failed at the planning stage. The teams meet in their final pool game, on 13 October.

The crucial score on Saturday came on 58 minutes. Japan, gaining in confidence, attacked in waves, the timing of passes and runs by support players taking them into space – and when Ryoto Nakamura’s break took his side into Ireland’s 22, Timothy Lafaele’s slick pass allowed the replacement Kenki Fukuoka the space to score in the left corner and give the hosts the lead for the first time.

It demanded a response from Ireland and they played as they know best, driving hard, taking play through phases and waiting for a penalty to kick to touch. It came but Japan read the throw and stole the ball, and slowly but steadily the air went out of the men in green.

Play Video 0:54 Japan fans celebrate wildly after stunning Ireland in Rugby World Cup – video

Japan had been camera shy against Russia on the opening night, unused to the attention and uncomfortable in it, but here they revelled in the spotlight. Their lead was four points but they remained uninhibited, Matsushima leading a breakout from his own line before a scrum in the home 22 was the base for another counter.

It was not just the humidity that was foreign to Ireland but the refusal of their opponents to stick with what they had. Tamura’s third penalty nine minutes from the end, after Conor Murray had overstayed his welcome on the wrong side of a ruck, meant Ireland were playing for a draw but still Japan came at them, Fukuoka denied a second try after a 60-metre interception when he took the inside track rather than the outside and was hauled down by Keith Earls.

It was Ireland, though, who were caught short. They had started strongly, Jack Carty twice using advantage after they were awarded a penalty in Japan’s 22 to launch kicks that discomfited the defence and yielded tries for Garry Ringrose and Rob Kearney.

Ireland had a final chance with 12 seconds to go when Isileli Nakajima knocked on just short of the line. Joey Carbery opted to kick the ball dead and take the bonus point.