Outside a train station near Tokyo, hundreds of people cheer as Sohei Kamiya, head of the surging nationalist party Sanseito, criticises Japan’s rapidly growing foreign population.

As opponents, separated by uniformed police and bodyguards, accuse him of racism, Kamiya shouts back, saying he is only talking common sense.

Sanseito, while still a minor party, made big gains in July’s parliamentary election, and Kamiya's "Japanese First" platform of anti-globalism, anti-immigration and anti-liberalism is gaining broader traction ahead of a ruling party vote Saturday that will choose the likely next prime minister. 

Anti-immigrant policies, which allow populists to vent their dissatisfaction on easy targets, are appealing to more Japanese as they struggle with dwindling salaries, rising prices and bleak future outlooks.

The populist surge comes as Japan, a traditionally insular nation that values conformity and uniformity, sees a record surge of foreigners needed to bolster its shrinking workforce.

In September, angry protests fueled by social media misinformation about a looming flood of African immigrants quashed a government-led exchange program between four Japanese municipalities and African nations. 

Even the governing party, which has promoted foreign labour and tourism, now calls for tighter restrictions on foreigners, but without showing how Japan, which has one of the world's fastest-aging and fastest-dwindling populations, can economically stay afloat without them.

Japanese people tolerate foreigners who respect the "Japanese way", but those who cling to their own customs are not accepted because they intimidate, cause stress and anger the Japanese, Kamiya said at the rally in Yokohama, a major residential area for foreigners. 

Kamiya said the government was allowing foreign workers into the country without numerical limits only to benefit big Japanese businesses.

"Why do foreigners come first when the Japanese are struggling to make ends meet and suffering from fear?” he asked. 

He rejected claims of racial discrimination.

All five candidates competing in Saturday's governing Liberal Democratic Party leadership voting to replace outgoing Shigeru Ishiba as prime minister are vowing tougher measures on foreigners. 

One of the favourites, former Economic Security Minister Sanae Takaichi, a hardline ultra-conservative, was criticised for championing unconfirmed claims that foreign tourists abused deer at a park in Nara, her hometown.

Takaichi later said she wanted to convey the growing sense of anxiety and anger among many Japanese about "outrageous" foreigners. 

Japan has a history of discrimination against ethnic Koreans and Chinese, dating from the colonialist era in the first half of the 20th century. 

Some of that discrimination persists today, with insults and attacks targeting Chinese immigrants, investors and their businesses. 

Saki Yagi, originally from Vietnam, who has lived in Japan for more than a decade, told the Associated Press that it was tough for her when she first arrived. 

It was not only the language barrier, but being verbally abused by her Japanese colleagues at work. 

"I still cannot fully get over it", Yagi said. 

Japan’s foreign population last year hit a new high of more than 3.7 million. 

That's only about 3% of the country’s population. Japan, which also promotes inbound tourism, aims to have 60 million visitors in 2030, up from 50 million last year.

The foreign workforce tripled over the past decade to a record 2.3 million last year, according to Ministry of Health, Labor and Welfare statistics. 

An increase of 300,000 from a year earlier was twice the projected pace - many work in manufacturing, retail, farming and fishing.

Even as the foreign population surged, only about 12,000 foreigners were arrested last year, despite alarmists’ claims that there would be a crimewave, National Police Agency figures show.

The pro-business ruling Liberal Democratic Party in 1993 launched a foreign trainee programme and has since drastically expanded its scope in phases but has been criticised as an exploitive attempt to make up for a declining domestic workforce. 

It will be renewed in 2027 with more flexibility for workers and stricter oversight for employers.

Many Japanese view immigrants as cheap labor who speak little Japanese, allow their children to drop out of school and live in high-crime communities, says Toshihiro Menju, a professor at Kansai University of International Studies and an expert on immigration policies. 

He says the prejudice stems from Japan's "stealth immigration system" that accepts foreign labor as de facto immigrants but without providing adequate support for them or explanation to the public to foster acceptance.

A Sanseito supporter in her 50s echoed some of these views but acknowledged that she has never personally encountered trouble with foreigners.

Meanwhile, Japan faces real economic pain if it doesn't figure out the immigration issue. 

The nation will need three times more foreign workers — or a total of 6.7 million people — than it currently allows, by 2040 to achieve 1.24% annual growth, according to a 2022 Japan International Cooperation Agency study. 

Without these workers, the Japanese economy, including the farming, fishing and service sectors, will become paralyzed, experts say.

It is unclear whether Japan can attract that many foreign workers in the future, as its dwindling salaries and lack of diversity makes it less attractive.

AP Video shot by Mayuko Ono