The Wallaroos tumbled 12-10 on the Gold Coast tonight as the victims of impatience, flustered errors and the inspirational tackling of the Japanese.
Wallaroos fullback Lori Cramer had a chance to steal a win at the 77-minute mark but the normally reliable goalkicker sprayed a shot at penalty goal from a gentle angle..
There was a mild moment of protest that the Japanese players had come off the tryline as she prepared to kick but the issue quickly dissolved.
Skipper Shannon Parry lamented the Wallaroos were "our own worst enemies" and she was spot on.
"We failed to execute on a number of occasions and I'd hate to know the turnover count," Parry said.
"We've only been together for 10 days as a new squad so we are in a learning phase. I'm just glad this lesson happened now not at the World Cup later in the year.
Added coach Jay Tregonning: "It was 100 per cent not down to that last kick. We had a number of opportunities well before that which we didn't take."
Great credit goes to Japan, who will improve on their world ranking of 12th after upsetting the Wallaroos, ranked at No.5.
The visitors were the outsiders in the Tri-Nation tournament staged this month in south-east Queensland but they upset both Fijiana and the Wallaroos.
The pressure applied by the rushing Japanese defence rattled the Australians, either into a mistimed pass, an inferior position behind the advantage line or into a vulnerable position for hungry ruck workers to attack the ball.
The Wallaroos sang the national anthem in two languages in a first for them that was warmly embraced by the midweek crowd and the players alike.
The anthem sung in the language of the Yugambeh country, to recognise the traditional owners of the land on which the game was played at Bond University, was led by the wonderful voices of the Yugambeh Youth Choir.
The Wallaroos sang it arm in arm and had learnt the words in the lead-up. The entire 23-strong squad swaying in unison in a serene show of unity was unscripted.
"It was a massive stepping stone for Australian sport and the Wallaroos. It was a really proud moment for us. We were 100 per cent into learning the words and paying respect to elders of the land on which we played," Parry said.
After the promising signs shown in last Friday night's 36-19 win over Fijiana, the opening 50 minutes of this Test against Japan were a disappointment.
The impatience to the Wallaroos play as they pushed passes and rushed their plays was the antithesis of the mood they needed to harness against the busy, swarming line of Japanese defenders.
The Wallaroos had a size advantage but rarely used it but for No.8 Grace Hamilton making several strong charges in that period.
There was far too little of that direct play when prop Eva Karpani needed to be unleashed more.
Instead, the Wallaroos were mesmerised by the few inroads they made out wide and kept flinging the ball hopefully without first earning the right by punching runners hard at the line up the middle.
Outside centre Georgie Friedrichs and winger Mahalia Murphy made incisive runs with speed and confidence but were turned into nothing more.
Another strong Murphy run approaching half-time was squandered by impatience. Instead, of a calm play with quick ruck ball when she was halted, a pass flung at Ivania Wong was intercepted and booted downfield.
If not for an incredible chase by lanky Wallaroos lock Kaitlan Leaney, it would have cost a try. Leaney chased winger Komachi Imakugi more than 80m in all before she fell on the bouncing ball to save the day 5m from her tryline.
Early in the second half, prop Madi Schuck held up the Japanese over the line for another vital save.
At the 48-minute mark, the Wallaroos made an error too many. Flyhalf Arabella McKenzie spilt a pass in midfield that just reached her from halfback Iliseva Batibasaga. She tried to turn it into a flip-on between her legs.
Japanese flyhalf Ayasa Otsuka swooped on the loose ball and ran in the try. She converted for 7-0.
It was the jolt the Wallaroos needed because everything became more urgent and direct from that point.
Flanker Emily Chancellor kicked and chased strongly to set up a bridgehead deep in Japanese territory. Hooker Ashley Marsters mauled the ball over the tryline for 7-5.
The Japanese bounced back by applying more pressure of their own and Japanese flanker Kyoko Hosokawa sliced over from close range for 12-5.
The Wallaroos had deliberately held back their top front-row so Liz Patu, Bridie O'Gorman and Adiana Talakai could make their impact with size and a more direct game over the closing stages.
Talakai speared over off a well-working rolling maul off a lineout win. Cramer had no joy with the conversion or the penalty goal to follow and was quickly consoled by teammates after full-time.
Hamilton and Friedrichs were both impressive again. McKenzie is a quality No.10 but this was a night to be a shrewd game-controller and she will know she has plenty to work on.
Japan 12 (Kyoko Hosokaw, Ayasa Otsuka tries; Ayasa Otsuka con) beat Australia 10 (Ashley Marsters, Adiana Talakai tries)
WALLAROOS V JAPAN TEAMS
Wallaroos (1-15): Madison Schuck, Ashley Marsters, Eva Karpani, Michaela Leonard, Kaitlan Leaney, Emily Chancellor, Shannon Parry (c), Grace Hamilton, Iliseva Batibasaga, Arabella McKenzie, Ivania Wong, Pauline Piliae, Georgina Friedrichs, Mahalia Murphy, Lori Cramer
Replacements: Adiana Talakai, Liz Patu, Bridie O'Gorman, Sera Naiqama, Piper Duck, Layne Morgan, Trilleen Pomare, Jemima McCalman
Japan (1-15): Saki Minami (c), Asuka Kuge, Yuka Sadaka, Kie Tamai, Otoka Yoshimura, Iroha Nagata, Kyoko Hosokawa, Mateitoga Bogidraumainadave, Moe Tsuki, Ayasa Otsuka, Komachi Imakugi, Mana Furuta, Rinka Matsuda, Hinano Nagura, Ria Anoku
Replacements: Hinata Komaki, Misaki Suzuki, Makoto Lavemai, Maki Takano, Mio Nishimura, Kotone Yasuo, Sakurako Hatada, Yuki Ito
HOW TO WATCH WALLAROOS V JAPAN
The Wallaroos' Test with Japan will be shown LIVE on Stan Sport.
Coverage will be ad-free and begin from 4:50 pm (AEST), with the game slated for a 5:00 pm kick off.