Former Wallabies fly-half Berrick Barnes says the sell-out crowd awaiting the final of Rugby World Cup 2025 is "just reward" for how far the women's game has come in recent times.

Barnes made 51 Test appearances for Australia in a career that included playing at Rugby World Cups in 2007 and 2011, where the Wallabies were latterly beaten in the semi-finals by the All Blacks.

The 39-year-old has been back in the Rugby World Cup fold these past few weeks as an assistant coach for Japan's Sakura 15s, so has been watching the growth in the women's game from up close.

Japan were beaten by an impressive Ireland side in their opening game of the tournament, and as such were always on the back foot to qualify for the quarter-finals as there was still a second-round game against the six-time champions New Zealand to come.

"Ireland to be fair were very, very good that day," Barnes says. "That's the margins in the competition."

Japan lost to the Black Ferns which ended their chances of progression, but were able to beat Spain in a thriller in York in the final round of the pool stage. After the game, there was the usual scenes of both teams coming together to interact and celebrate each other, as well as speaking with the fans who had come to watch.

"That's the difference with women's sport; the quality of relationships off the field," Barnes says. "You see the respect and the care there, and it's really nice."

The former fly-half knows that kind of interaction will be tough when the final two games take place at Allianz Stadium in Twickenham on Saturday, but says the size of crowd is nothing more than the game deserves.

"You know, 80,000 at Twickenham is going to be just reward for where the game's gone and how much it's growing," he said.

There are four teams left standing, with New Zealand taking on Canada in the first semi-final on Friday night, while England take on Six Nations rivals France the following day. Barnes feels England is the team to beat at Rugby World Cup 2025, but says each semi-final team is capable of beating the other based on recent meeting.

"It's England's to lose," he said. "They've been the best team for the last eight years really, they've just lost two finals in small margins.

"If they can cope with the pressure and allow their forwards to use their maul and kick smartly, they're going to be really hard to beat.

"New Zealand seems to have the wood over England in big games but England has the wood over France, and Canada can beat a few of those teams too, but then they haven't been able to get over England.

"It's going to be interesting how they play out."

Barnes has been impressed by several stars at this tournament - including Jorja Miller who he described as a "rare talent" - but though his countrywoman were unable to progress past the quarter-finals, he is hoping this tournament can be the springboard to keeping their young talent in the game and not losing them to other sports in the country.

"Caitlyn Halse has been a real find," he said. "There's some real talent there, our key thing will be probably to keep them in rugby and not lose them to league.

"The challenge is keeping them in the game, and this next cycle is crucial to the next World Cup. We've got some really good talent there."

Whether or not Barnes is involved in that Rugby World Cup 2029, he says he has enjoyed his time coaching on-and-off with the Japan side under head coach Lesley McKenzie.

"It's been a great ride," he said. "I got to see a lot of the players across the last three or four years which has been nice.

"It was brilliant. We don't get to play as many games as maybe some of the other nations, so that's where we're a bit poor, but in terms of training quality and the effort put in by the players, it's probably second to none.

"Lesley McKenzie runs a great programme. She's been with the girls for six years now so she knows what makes them tick and how to push and pull and that sort of stuff. She did a wonderful job."

Next, Barnes will return to Japan where he is working as an assistant coach in a full-time capacity with Panasonic Wild Knights, a team he previously played for in. As a result, the Australian has spent a lot of time in the country and has grown fond of Japan's rugby fans.

"The fans are fantastic, they're very rusted on, they're very loyal," he said. "A lot like their people; they're good people who care."