Even before their famous push to the quarter-finals, George Smith knew Japan's performance at the Rugby World cup would be transformative for the sport in the country.
The former Wallabies flanker will return to Japan to continue his rugby career next season, joining the coaching staff at Suntory - the same cub from which he was sacked in 2018 after an alleged assault on a taxi driver.
But Smith has an enduring love affair with the game in Japan and said the Brave Blossoms' victory over Ireland alone, "justified" the country hosting the game's biggest showpiece.
What their subsequent win against Scotland and push into the quarter-finals would do for the game in the region would be massive.
"To win that game (against Ireland) just justified why they would host the World Cup there," Smith said.
"Then also the stuff outside of that. That funding that's going to be generated into rugby moving forward - they have a competition in 2021 that they're looking to facilitate there - that's just going to give a big boost as well.
"Rugby in Japan has always been consistently all right but now that they've had sold out crowds each and every game they've played there and the way the Japanese have embraced the game, it's huge.
"To win that game and to have the juniors in the rugby rooms, especially with the tier one teams, that's been huge for them."
Japan is already a huge market for international stars given the contract money available and the country is only likely to become more attractive with an elite 12-team domestic competition planned from 2021 which it's expected could attract revenue of as much as 50 billion yen ($A673 million) through broadcast rights and sponsorship.
And while there has always been company support for the sport, Smith said the World Cup had helped capture the attention of the general population, who would now continue to embrace the game.
"It's always been supported by companies in Japan, it's always been pushed that way but now the public have grabbed on to it and really appreciate the values of rugby and the traditions of rugby and the athletes that are playing the game over there," Smith said.
And with the sport to be further showcased through sevens at the Tokyo Olympics next year, there was opportunity to build on the popularity.
"And that's not just in the men's ranks, it's in the women's as well," he said of the popularity of the sport to the Japanese people.
"To be an Olympic sport as well, it's definitely helps them."
Whether a repeat of their 2015 World Cup win over South Africa is on the cards or not, Smith knows the Japanese deserve their spot in the final eight.
"I don't think anyone outside of the Japanese team thought that they'd be in this position," he said.
"But I always thought that this game (against Scotland) would be a crucial one for them in reaching the quarters and I'm very pleased for them.
"I know a lot of the players in that squad and they've worked extremely hard to be in the position they are."
Japan take on South Africa in the last of the quarter-finals at Tokyo Stadium on Sunday, October 20, kicking off at 9:15pm AEDT and broadcast LIVE on Foxtel and via RUGBY.com.au RADIO, Rugby Xplorer and Amazon Alexa.
