The Irish took over the area around Shin-Yokohama train station tonight. There were thousands of them spilling out of the bars and cafes on the way to Yokohama Stadium and inside this massive arena.

Most of them were dressed in green - some in unique fancy dress. All were there for the craic, a bit of fun, before their nation kicked off against Scotland. It was orderly but the beers were flowing and soon the songs came.

It was close to the exact opposite of the attitude undertaken by Joe Schmidt's team on a muggy late afternoon in this city just south of Tokyo. Ireland the rugby team aren't here for a laugh; they're here to do something they've never done before, and that's win a Rugby World Cup knockout game for the first time and go on and do it again and again.

On this evidence they look capable of going a long way in this tournament because they began their campaign with the cold efficiency of a butcher, their victims a Scotland team which saw space on the field but had no idea how to make the most of it except by kicking to it.

Ireland's Conor Murray, right, congratulates teammate Andrew Conway after he scored their fourth try. Photo / AP
Ireland's Conor Murray, right, congratulates teammate Andrew Conway after he scored their fourth try. Photo / AP

Gregor Townsend's men were disappointing but Ireland did a job on them. First they were tenderised by the powerful and extremely well-drilled pack – the first three tries were scored by tight forwards - and then they were cut to pieces as a misty rain came down.

Their first-five Finn Russell was their only player who displayed any form of creativity. Unfortunately for him he didn't have the pack or midfield powerful enough to support him.

Ireland, with tough, experienced men such as Rory Best, Peter O'Mahony and Cian Healy in their pack, look like a better version of the Springboks, and, if the rest of the Pool A and Pool B matches go as expected, the Boks will play the Irish in a quarter-final at Tokyo Stadium on October 20 and the South Africans will be up against it.

Scotland, should they beat Japan, would play the All Blacks at the same venue a day earlier. A Scottish victory over the hosts at Yokohama Stadium on October 13 is not a given.

On the evidence of this weekend, an Ireland v South Africa knockout match would be epic in its brutality and possibly pace as well. A match-up between wings Cheslin Kolbe and Jacob Stockdale would not lack energy.

Probably the politest thing to say about an All Blacks and Scotland quarter-final is that, unless the Scots improve significantly, it probably wouldn't be as close.