Both teams go into the match with two wins from three games and the permutations are simple: the winning team goes through to the quarter-finals and the losers go home.
The Pumas have been to World Cup semi-finals in 2007 and 2015 but, echoing sentiments expressed by his boss Michael Cheika, assistant coach Juan Martin Fernandez Lobbe was focusing purely on Japanese strengths on Sunday.
"They are a team that has qualified for the quarter-finals in the last Rugby World Cup, a team that we know is going to be very tough," Lobbe said, a day after Argentina thrashed Chile 59-5.
"It is a dynamic team, with a clear idea of what they want, a very, very difficult opponent. They are a very well-prepared team, with a very good coach."
Although Japan reached the quarter-finals on home soil at the last World Cup while Argentina flopped out in the pool stage, the Pumas stand four spots above the Brave Blossoms in the world rankings.
In the last two years, Argentina have beaten the All Blacks in New Zealand, England at Twickenham and the Wallabies in Sydney, while world champions South Africa edged the Pumas by a single point in Johannesburg in late July.
Japan this year, by contrast, have lost to Samoa and Fiji, were beaten twice by a New Zealand A team, and went down 42-21 to Italy before arriving in France.
Lobbe, who played openside flanker for the 2015 Pumas team that reached the last four of the World Cup, nevertheless said he was expecting a major challenge from the Japan pack at Stade de la Beaujoire.
"It is a good scrum... solid, with quick ball," he said.
"We are preparing for a great battle since they have good set-pieces. We know that they will want to be among the top eight and so are we. It's going to be a great battle.
"We need to be prepared to grab the opportunity with both hands."
