The Wallabies could have wilted in an Osaka sweatbox, but captain Harry Wilson was thrilled they found a way to ensure new coach Les Kiss began his tenure a winner.
And the back-rower praised his coach for a crucial halftime intervention when, down a man after a 20th-minute red card to lock Miles Amatosero, it appeared Japan were set to notch a historic first win over the Wallabies.
But in high humidity and with temperatures pushing 30 degrees late into the night, they went toe-to-toe with Eddie Jones's side.
A late Taniela Tupou try was enough for a 35-32 win, despite plenty of nervous moments.
"Once we had the red, we knew we were under the pump and got a bit lucky that it was halftime," Wilson said.
"The coaches gave us a good plan of how to play with the red card for the next 11 minutes, and when we got that second lock back we had that confidence. But in saying that, they just didn't go away, they were on us all game."
Amatosero is facing weeks on the sideline after making high contact in a clean-out on Japan captain Warner Dearns.
In his starting debut, the NSW Waratahs firebrand paid the price for not tucking his arms when he rushed into the ruck and struck the skipper as he fell in a potentially mitigating factor.
Yellow card for Miles Amatosero!#JPNvAUS #Rugby pic.twitter.com/eR79Hj36bc
— All Things Rugby (@AllThingsRugbyX) August 8, 2026
Up 14-7 and within range of scoring again, the Wallabies were instead down a man and then level at halftime.
The visitors never had it on their terms but, thanks to some brilliant backline moments, bench impact from front-rowers Tupou and Angus Bell and another strong game from lock Josh Canham, they escaped ahead of a rematch in Townsville on Saturday.
There were no injuries, but the week spent in sweltering Osaka would have taken a toll, and Kiss will monitor his stocks when the side returns to Brisbane late on Sunday.
After six straight losses it was the Wallabies' second consecutive win, but far less fluent than what they produced against Italy in Perth in Joe Schmidt's farewell last month.
Stopping his press conference after only answering questions from Japanese media, Jones lamented fundamental mistakes in the tight loss, but admitted he was surprised by the ease at which his men made ground around the ruck.
Australia had scrambled well, tackling at 89 per cent despite making 86 tackles to Japan's 54 in the first half.
But it's an area they'll need to plug when greeted by more conducive attacking conditions on Saturday afternoon in Townsville.
"To get a win here in these conditions, we're happy, but there's areas to improve next week," Wilson said.
"That's the beauty of a two-game series, to get to go to battle again.
"We'll have a few areas to review very accurately and make sure we can fix for next week."
