Ireland coach Andy Farrell says Japan are "bang in form" and pose a threat, but Eddie Jones' side will need something special to topple a team on a five-match win streak when they meet on Saturday.
The two sides clash on neutral territory at the beachside town of Newcastle, north of Sydney, in round two of the Nations Championship with both of them on a high.
Japan are brimming with confidence after toppling Italy 27-10 in Tokyo last weekend while Ireland pulled off a stunning last-gasp 33-31 victory over Australia in Sydney, rallying from behind four times.
Farrell has swung the axe with his eye on protecting key players ahead of a blockbuster clash with New Zealand at Eden Park on 18 July with nine changes to the starting side.
But he is not taking Japan lightly, despite the teams being separated by nine places in the world rankings. Ireland are ranked three and Japan 12.
"For anyone who's seen their games, they are a team that's bang in form," said the Englishman.
Farrell pointed to not just the Italy match but also Japan's 38-31 loss to the Maori All Blacks late last month.
"I mention the Maori game of how they played against them, and obviously the confidence that they took from that is what they took into the Italian game," he said.
"And we all know how difficult Italy are these days to play against.
"I thought Japan dominated the game from start to finish last week, so the confidence that they're going to bring over to Newcastle here is going to be the test that we're after."
Only six players remain from Ireland's win over the Wallabies – backs Stuart McCloskey, Jamie Osborne and Jimmy O'Brien and forwards Tom O'Toole, James Ryan and Jack Conan.
Tadhg Beirne will lead them out as captain for the first time, with Dan Sheehan rested.
DIFFERENT THREAT
Despite fielding an under-strength side, Ireland are heavy favourites, having won five tests on the trot, beating Australia, Scotland, Wales, England, and Italy.
They have a dominant record against Japan, claiming victory in 10 of their 11 meetings with the Brave Blossoms' sole win during the 2019 Rugby World Cup when they caused a 19-12 upset.
But Japan will take heart from their performance against Italy, where they were strong at the scrum and maintained 100 per cent lineout success, a crucial set-piece edge.
Jones, who is back at the helm after a four-match ban for abusing match officials on a tour of Australia this year, said he was encouraged by what he saw.
"I think everyone was pleased with the first week of the Nations Championship, it produced some great rugby," said the Australian.
"We were lucky enough to be part of it and this week we play a very strong team in Ireland, who we know have got a massive work ethic.
"Ireland are a different opposition, they present different threats. They're a much more possession-based team than Italy were, so we've worked a lot on our defensive quality."
He has kept faith with university student fly-half Ryunosuke Ito after he impressed on his debut against Italy, retained to start alongside scrum-half Naoto Saito.
"He's a young 10, he's going to have his ups and downs but we've got a team that's going to support him," said Jones.
Taira Main replaces Kippei Ishida on the left wing in Japan's only other change.