TOKYO (AP) -- A fringe far-right populist party Sanseito was one of the biggest winners in the weekend's upper house election, attracting many voters with "Japanese First" platform that included calling for tougher restrictions on foreigners and the curtailment of gender equality and diversity policies.

Sanseito added 14 seats in Sunday's vote to the one seat already held by its leader in the 248-member upper house, the less powerful of Japan's two-chamber parliament.

The surge in the party's popularity came amid the backdrop of a historic loss by the long-governing conservative coalition of Prime Minister Shigeru Ishiba, with Sanseito attracting frustrated voters struggling with economic woes.

Sanseito leader Sohei Kamiya said Tuesday that he has no interest in forming an alliance with conventional parties like Ishiba's Liberal Democratic Party, or LDP.

Kamiya said he is open to cooperating with other emerging parties, but he's expected to wait in the hopes of gaining more seats in the more powerful lower house. His ambition is to have more influence to possibly form a multiparty coalition like those in Europe.

Sanseito, which translates to "Participate in Politics," started in 2020 when Kamiya gathered people on YouTube and social media to create a political group to attract voters discontent with conventional parties.

The group began to grow as its members started winning seats in local assemblies, stepping up its presence and grassroots support base.

After the start of the coronavirus pandemic, his online approach quickly got traction, fueled partly by an anti-vaccine stance.

Sanseito achieved a foothold in national politics in 2022 when Kamiya won a six-year term in the upper house. The party won three seats in the October election in the lower house.

The party's 15 seats in the upper house seem like a tiny share compared to the 122 held by Ishiba's governing coalition, but Kamiya has been steadily reaching a much larger audience.

Sanseito has gained more than 100,000 YouTube subscribers over the past few weeks to nearly 500,000, compared to the the LDP's 140,000.

Sanseito party stood out from Japan's other parties, with a tough anti-foreigner stance as part of its "Japanese First" platform, apparently inspired by U.S. President Donald Trump's "America First" policy.

Under his slogan, Kamiya proposes a new agency to handle regulations on foreigners. During the election, the party campaigned for stricter screening for allowing Japanese citizenship and to exclude non-Japanese from welfare benefits.

Critics say that the party's stance has encouraged the spread of xenophobic rhetoric in the election campaign and on social media, prompting other ultraconservative candidates to be outspoken. A typical claim is that a rapid increase in foreign workers has hurt Japanese workers' wages and that foreigners use a large share of welfare benefits and have made Japanese society unsafe.

That resonated with many Japanese, even though most foreign residents pay taxes and social security as required, and only account for about 3% of both Japan's total population and of welfare benefit recipients.

His xenophobic views, antisemitic remarks and emphasis on Japan's ethnic purity have alarmed human rights activists and many experts, prompting protests.

Kamiya's party, and another big winner, the Democratic Party for the People, which pushed for an increase of "take home wages," attracted workers who feel frustrated and ignored by conventional parties.

Kamiya, a former Self-Defense Force reservist and an assembly member in the western town of Suita, promotes an anti-vaccine and anti-globalism platform, while backpedaling on gender equality and sexual diversity. He has repeatedly talked favorably about Trump for taking bold measures.

During his campaign, he said that Trump's leadership is part of a growing anti-globalism movement in the West, and that "we share the same concern."

He also told a party leaders' debate that Trump policies are for protecting U.S. national interest and are good examples that Japan should follow. Kamiya also supported Trump move to repeal decarbonization and diversity, equity and inclusion policies.

Kamiya, a fiery speaker, is also known for stirring controversy and has become a target of scrutiny as his party gained attention.

He has blamed the government's gender equality policies for triggering Japan's declining birth rate and population.

Kamiya, who opposes allowing a female-line emperor, was also criticized for suggesting that the imperial family would have to turn to concubines, if the government was too slow in taking measures to ensure a stable succession.