“I wish there were more Japan-born players on the team, but it’s OK because they all feel that they are Japanese,” said Moteki, who lives in Tokyo. “It’s like it was during the Greater East Asia Co-Prosperity Sphere, when Koreans and others volunteered to serve in the Japanese military.”

Between 1930 and 1945, imperial Japan placed puppet leaders in positions of authority in countries and regions that it invaded and occupied, from Manchuria in the far north to Cambodia, Vietnam and Indonesia. Tokyo declared the union under its control was designed to be a self-sufficient “bloc of Asian nations led by the Japanese and free of Western powers”.

Moteki was particularly pleased that a Korean-born player had opted to play for the Brave Blossoms, with 25-year-old Koo Ji-won playing as prop.

“It is natural,” he said. “Basically, Koreans do not hate us, they have just been ideologically brainwashed in the last few years and I think this is good for Asian rugby.”

As well as a Korean-born player, the 31-strong Japanese squad is made up of a number of naturalised Tongans, Samoans, New Zealanders, Australians and South Africans. Captain and New Zealand-born Michael Leitch is 30 years old and has played for Japan 63 times, while coach Jamie Joseph is a Kiwi who represented the All Blacks over a period of four years.

There were 124.78 million Japanese nationals at the start of 2019, a decline of more than 433,000 from the same period of the previous year. The number of foreigners living in Japan, however, has gone in the other direction. There were 2.67 million non-Japanese living in the country, up 169,543 on the previous year and surpassing 2 per cent of the total for the first time.

Recognising that it has a serious demographic problem on its hands – not enough children are being born to young couples while medical advances are enabling people to live longer – the Japanese government has introduced a scheme to relax visa regulations for foreign workers to take up blue collar jobs.

Conservatives, however, have railed against the new scheme, claiming that foreign workers will take local people's jobs, that outsiders will disrupt “social harmony” – and some even claiming that opening the nation's doors to potential regional rivals, such as China, could even damage national security. The solution that many on the right of politics would prefer is the development of robots to meet any shortfall in human workers.

Regardless, the demographic issues seem to have been put aside for the Rugby World Cup.

“About half the team was born abroad, but the amazing thing for me is just how hard they are all fighting for Japan,” said Yoichi Shimada, a professor of international relations at Fukui Prefectural University. “It really is quite impressive.”

“I also believe this is highly symbolic because the question of the nationality of the players has been raised in conservative media here – but they have chosen to highlight how honestly and enthusiastically they all sing the national anthem before the start of each game,” he said. “They sing it loudly and proudly.

“It is also clear to me that they are all speaking perfect Japanese, although I do fear that might cause problems for the Korean-born player on the team,” he said. “Given the Koreans’ recent anger towards anything Japanese, I do worry that he could be a target of criticism or worse.”

Ken Kato, a businessman and paid-up member of the ruling Liberal Democratic Party, admits to never having been much of a rugby fan, but says he has also been caught up in the excitement of the tournament.

“These foreign-born players have chosen to represent Japan, they speak the language and know our customs, so I believe they are contributing to Japanese society,” he said.

“They are now our countrymen, no matter where they came from originally – and you can see that in the way they sing the national anthem.

“I’m not a big believer in being Japanese based on a person’s blood, it’s more about how a person accepts our culture and contributes in a positive way to our society,” he said.