Double will be the key word if Japan is to pull off an upset Saturday to match the Brighton Miracle.
For if the Brave Blossoms are to repeat their win four years ago over South Africa by beating Ireland, currently ranked No. 2 in the world, it will be down to their ability to dominate in terms of double collisions and double actions.
Double collisions describe the two-man hits that the Brave Blossoms will employ to stop the powerful Irish forwards, while double action is the ability to gain further yards with ball in hand.
"They are big men and enjoy playing with ball in hand," Japan defense coach Scott Hansen said Friday of props Cian Healy and Tadhg Furlong, though the description applies to the whole Ireland pack, which laid the foundation for its 27-3 win over Scotland last week.
"The key thing will be to be smart and have high situational awareness as they like to get the ball in hand in scoring areas," Hansen said.
Discipline will also be crucial in making sure the double hit is both legitimate and effective, because as prop Keita Inagaki pointed out, Tier 1 sides know how to punish teams.
"Against Tier 1 sides you only get a few chances to score. So you cannot afford to concede points," Inagaki said after his team's captain's run at the match venue.
Japan will also need to be patient, as much of the buildup to Saturday's game at Shizuoka Stadium Ecopa has centered on Ireland's ability to hold onto the ball.
"We know they are a world-class side with a highly efficient attack," Hansen said.
"They hold onto the ball longer than any side in world rugby and put together multiple phases. So the challenge will be how to get the ball back."
And when Japan does get the ball it also needs to make sure it makes the most of it, as exemplified by Kazuki Himeno.
"It's his unwillingness to stop with ball in hand," said head coach Jamie Joseph when asked to explain what the back-row forward brings to the team.
Himeno is a master of the double action, and his ability to release the ball in the tackle and then regather it when the defender slips off him will be key to getting over the gain line and unlocking the Irish defense.
Kotaro Matsushima will certainly be hoping that occurs.
Having lived up to his pre-match prediction that he would score three tries against Russia, the Japan wing has said he will cross the chalk twice against Ireland.
"If the ball goes wide, there will be scoring opportunities," he said.
But that means Japan needs to hold its own against an Irish pack that has some local knowledge.
Scrum coach Greg Feek splits his time between Ireland and Japan where he works with the Top League's NEC Green Rockets and he admits to having "good insight and a good feel of (Japan's) scrum and general play."
Much of the buildup has been dominated by comments made by prop Yusuke Kizu, who is not even in the matchday 23, that the Irish use illegal tactics in the scrum.
Both Joseph and Feek said Kizu may have been intimidated by the scale of the news conference at which he made the remarks, though they differed slightly as to whether the young prop was actually right.
"Yes, at times they are illegal, but at all times they are a very strong scrum," Joseph said.
Fellow former All Black Feek disagreed, saying, "Our mantra is we are the most disciplined team in world rugby and how this team goes about things in terms of discipline is world class."
The two teams last met in 2017 with Ireland, missing a number of its top players who were away with the British and Irish Lions, winning 50-22 in Fukuroi and 35-13 in Tokyo.
But center Garry Ringrose says things have changed.
"They are a different beast from two years ago and we are under no illusion how much stronger and better they are," he said.
Matsushima agreed, saying, "There are things that are different tactically and we now have a much better understanding of that. We're now all on the same page as a team and that's the difference. We've grown in terms of our attack and the key will be patience."
A sellout crowd of around 50,000 will be hoping the Japan flyer is right.