His demand comes even though the fixture carries huge repercussions for the 2027 draw.
Rankings will determine which band Wales fall into for December’s seedings, and with Tandy’s men sitting 12th — only 0.32 points above Japan — the pressure of avoiding a slide into band three is obvious.
But the Wales coach was adamant his players must think solely about performance rather than mathematical outcomes.
“There’s lots around ranking points on this game, but ultimately as a team we’ve got to focus on ourselves and how we grow as a team,” said Tandy.
“We can’t start worrying on all the things we can’t control.”
The top six counties in the rankings at the time of the draw will be seeded in band one, with teams from sixth to 12th places in band two.
The next groups of six teams are then in bands three and four respectively.
At 12th place in the rankings, Wales are currently the final team provisionally in band two but would fall behind 13th-placed Japan into band three if the Brave Blossoms gain at least a draw in Cardiff.
READ MORE: Rees Lightning to Hit Japan . . . Louis Rees-Zammit Will Start First Test for Wales in Two Years
Japan then play 11th-placed Georgia in Tbilisi on November 22, while Wales complete their autumn series of games with difficult matches against giants New Zealand and South Africa, the nations ranked second and first in the world respectively.
The side who ends up in band three would face a tougher set of pool opponents based on the rankings.
The standings are calculated via a 'points exchange' system, with sides taking points off each other based on the result of the match.
Wales, however, can take encouragement from the fact they beat Japan the last time they played Eddie Jones' side - a victory which ended a record 18-match losing Test run - with a 31-22 success in Kobe in July.
That message forms the backdrop to a match in which Louis Rees-Zammit makes his first start for Wales since his NFL adventure.
READ MORE: Louis Rees-Zammit: “A Lot of Big Names Left After the World Cup – Now it’s Time to Change”
The 24-year-old wing returned from stints with the Kansas City Chiefs and Jacksonville Jaguars earlier this year and impressed off the bench against Argentina last weekend.
For Tandy, promoting him to the starting XV was uncomplicated.
“I think it was pretty straightforward,” he said.
“We know the quality he brings. It’s exciting. He’s been brilliant around the camp. He’s grown as a rugby player, he’s leading really well.
“He was brilliant last week coming off the bench. He was disappointed not to have one or two tries.”
Rees-Zammit’s game-breaking ability, Tandy believes, is precisely the type of threat Wales must harness as they attempt to end a miserable run of 10 consecutive home defeats.
“He can produce something. You need people who can break the game up. We’re fortunate to have someone like him available to us,” Tandy added.
“Him starting on the weekend is not just exciting for us coaches, but the fans as well.”
READ MORE: Judge for Yourself . . . Olly Cracknell Has Shown True Grit to Make it With Wales
Wales must, however, cope without captain Jac Morgan for the rest of the autumn after the flanker dislocated his shoulder scoring against Argentina.
The Ospreys flanker requires surgery and could miss the start of the Six Nations, robbing Wales of their defensive leader and most influential forward.
“It’s a pretty big blow,” Tandy admitted.
“At the end of the day, he’s a world-class player and he’s our leader. His performance on the weekend was outstanding.
“You see him in our environment, he’ll be sorely missed. Not just the player, but the man will be missed.”
Dewi Lake steps in as captain, as he did during Wales’ tour of Japan in the summer when Morgan was with the British & Irish Lions.
Alex Mann switches to openside, Alan Wainwright comes in on the blindside, and Olly Cracknell starts at number eight after making his debut last weekend.
Tandy has also freshened up the front row, with Nicky Smith and Archie Griffin replacing Rhys Carre and Keiron Assiratti, who drop to the bench.
Saturday’s visitors are no longer the unpredictable outliers of a decade ago.
Wales ended that losing streak in July, but the Brave Blossoms pushed them hard that day and have the weapons to cause problems again.
Wales will take confidence from that victory, but the stakes are undeniably greater this time.
A place in band two offers a clearer path in 2027; band three could condemn Wales to a far harsher pool.
