After brushing aside Scotland, it's time to face the hosts on Saturday morning, and Gavan Casey from our Pod Nations Predict team believes Ireland will put a big smile on the Mayor of Fukuroi...
"It's one area in which Ireland should dominate, but the harsher truth is that they're simply a superior outfit to Japan in virtually every area of the field."
Japan v Ireland
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Support from an unlikely source for Ireland
The Mayor of Fukuroi, Hideyuki Harada, told an assembly of Irish journalists on Friday morning that he will be supporting Ireland in their Pool A encounter against his native country.
Harada probably has an idea how to play to the gallery, all right: he has been re-elected six times since first taking office in January 2001.
Hosting Ireland's rugby scribes in Fukuroi's city hall, he was kitted out in an Ireland jersey and a beaming smile, the former which he claimed to have been wearing for the guts of a month. He told his curious guests of his admiration of Joe Schmidt as well as his favourite player, Johnny Sexton.
Sadly for Hadara, when Ireland line out against hosts Japan in his native city on Saturday, Sexton will be watching on just like him. And it's a testament to Schmidt that he can afford to give the reigning World Player of the Year a day off for a fixture of this calibre and still expect to depart Fukuroi with a victory.
It's a testament to the system he oversees, too, that the knock Sexton received against Scotland, and the subsequent doubts about his fitness, didn't set off panic alarms nationwide as they would have four years ago.
Carty can capitalise on Japan errors
The fact that Jack Carty - a player who got his first taste of international rugby seven months ago - can without doubt deputise for Sexton in such a meaningful fixture is a testament to his coaches at Connacht, but predominantly to himself.
In many ways, this encounter is made for the 27-year-old, and I suspect he'll put on a show at Shizuoka Stadium.
We saw it even in their nerve-stricken opener against Russia but more so during a thumping warm-up defeat to South Africa: when the ball is in the air, Jamie Joseph's Japan struggle to an almost comical degree. And Carty rarely needs a second invitation to throw his boot into the ball.
His is a cultured boot, too, though: that chip for Chris Farrell during the Scotland game was delectable, and his short game could cause arguably more consternation in that Japanese defence even than the high ball.
Japan know what's coming: after a flaky display against the Russians, Joseph has moved Will Tupou from fullback to the wing, where one would imagine he'll still be force-fed his fair share of box kicks, and where his poor defensive positioning could still be exploited by Carty's right foot.
It's one area in which Ireland should dominate, but the harsher truth is that they're simply a superior outfit to Japan in virtually every area of the field.
It could well play out similarly to the Scottish game, although it's difficult to conceive of Japan being so limp in front of a raucous home crowd.
Ireland's pack should systematically deconstruct that of its counterparts, though, and with an emphasis this week being put on putting the finishing touches on linebreaks - they made a promising 10 of them against the Scots - it's difficult not to see Schmidt's men killing the contest off before the hour mark.
Experience to beat inexperience with room to spare
Japan have been working towards trying to keep the ball in play for somewhere in the region of 50 minutes, the idea being that their biggest asset is their ability to wear teams down through sheer freneticism and a kind of maniacal intensity in attack.
They'll look to go wide as quickly and as often as possible, and even through the middle they have a world-class ball carrier in Amanaki Lelei Mafi who'll leave his dents.
It's inconceivable that they'll be fitter than Ireland, though, much of whose success over the past three or four years has been built upon a similar foundation of huffing and puffing until the opposition's door gives in.
Schmidt is giving the Japanese the respect they deserve by fielding something resembling a full team, but Ireland should have too much nous, too much ballast, and too much experience to be pipped by the exciting but inexperienced home side.
I'd expect Japan will sense that too before long and, with a potentially decisive Scotland clash looming, they might retreat into their shells a little bit in the final quarter if it's a two- or three-score game by that juncture.
The handicap is Japan +21.5, but I think Ireland might have a few more points to spare when the gong sounds on 80 minutes.
Back Ireland -21.5 v Japan @ [2.1]