New Delhi, July 23 -- Japan's far-right populist Sanseito party was one of the biggest winners in the weekend's upper house election, attracting many voters with its "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 s...