Two bonus-point wins, a rejuvenated Johnny Sexton breaking records and 20 tries in the bag. The World Cup is going as scripted for Ireland.

Ireland head coach Andy Farrell, who was defence coach under Joe Schmidt for that loss in Japan, had dismissed questions about any lingering scars of Shizuoka in the build-up to Saturday's Pool B win over Tonga in Nantes.

Naturally, even if they would not admit it, it would have been in the back of Irish minds after seeing off Romania in emphatic fashion, knowing that a slip-up against Tonga would incite panic before a couple of daunting Paris assignments against South Africa and Scotland.

Farrell took no chances. Retaining Sexton in a strong line-up that showed both Irish respect to Tonga and the desire to experience a bruising physical encounter before renewing hostilities with the Springboks, Farrell opted for momentum over rotation.

And while Tonga caused the world's number one side a few headaches, Ireland were never really in danger of experiencing a repeat of that humbling night in Japan.

With eight tries and an Irish scoring record for captain Sexton, who surpassed Ronan O'Gara to become his country's record points scorer, Ireland ultimately had too much for the Pacific Islanders.

Sexton attracted more plaudits, Bundee Aki continued his excellent form with another two tries, and after a fair bit of attention, the line-out functioned smoothly. Farrell said after the game that Ireland "aren't really into ticking boxes" but they have hit a lot of their targets so far.

But as with last week's win over Romania, the celebrations will be muted knowing the holders will be waiting for them at the Stade de France next week.

For Ireland, the first two games were always about getting the job done and building a healthy points total. The question now is, are they where they need to be for South Africa?

According to Farrell, improvement is still needed.

"I would hope we will be better because we'll certainly need to be when it gets to playing against a fantastic side in South Africa," said Farrell.

"We're not ready quite yet but we certainly will be.

"It's something that we've talked about quite a bit, obviously with the opponents that we knew we were going to face.

"We'll take that a step further this week and get the players to own that as soon as we possibly can.

"It's something that they're doing very well at this moment in time."

'It's the game all the outsiders have been looking forward to'

The Romania and Tonga games were not without their imperfections. While the line-out looked more robust against Tonga, Farrell and his coaching staff will almost certainly look to work on Ireland's scrum before facing a formidable South African pack.

But Ireland have made a habit of raising their game to face elite-level opposition. Last year's Test series win in New Zealand shows that, as does the titanic Six Nations win over France in Dublin.

Farrell's side also have relatively fresh memories of besting the Springboks in a brutal Aviva Stadium encounter in November.

Ireland will almost certainly downplay the significance of that game because South Africa in the World Cup are a different beast, but Ireland's journey over the past 18 months means they should approach Paris with relish, not fear. That wouldn't always have been the case in World Cups down the years.

"What a week to be involved in Irish rugby," said scrum-half Craig Casey, who made his World Cup debut off the bench against Tonga.

"It's the game that all the outsiders have been looking forward to for a good few years now since the draw came out.

"Obviously we had to get those first two games over the line and get two wins, but it's a huge week to be involved in. It's going to be great."

South Africa, who beat Scotland in their opener, play Romania on Sunday before they start planning for Ireland.

The Springboks have looked back to somewhere near their best lately, thumping the All Blacks in one of their warm-up games before taking care of the Scots in Marseille.

The holders have since lost hooker Malcolm Marx for the rest of the tournament to a knee injury, and while Farrell is still without his first-choice number number two in Dan Sheehan, Ireland have so far managed to avoid devastating fitness setbacks. Finlay Bealham came off just 10 minutes after being introduced against Tonga with a head injury, although Farrell later said the prop was in "great spirits".

But even with a clean bill of health, battling the three-time world champions under the Stade de France lights represents the greatest challenge this Irish juggernaut has faced.

"We knew this one was coming down the pipeline," said Iain Henderson, who was not involved in Ireland's 19-16 win over South Africa 10 months ago.

"It's probably our biggest challenge in a good while. I think everyone's excited about it. Fortunately for us, we're able to get into the meat of looking at them this week.

"All I can say is everyone is incredibly excited, irrespective of whether we'll be starting, on the bench or not involved. Everyone is buzzing."