Japan gets its first female leader, a conservative who favors a stronger military

Her election as prime minister comes days ahead of a possible visit to Japan by President Trump, with whom she shares conservative views and a hawkish stance on China.

Tokyo hopes that affinity will help heal ties that have been strained by Trump’s push to reorder global trade. Under the terms of an agreement struck in July, Japanese imports to the U.S. now face a tariff of 15% and Tokyo agreed to invest some $550 billion in the U.S. over the next few years.

In parliamentary voting for prime minister Tuesday, the 64-year-old Takaichi won a slim majority in the lower house on her first try with help from her new partner in government, the Japan Innovation Party. But she needed a runoff to prevail in the upper house after falling just short of a majority in the first vote.

That hiccup was a preview of the challenges Takaichi is likely to face as prime minister because her ruling Liberal Democratic Party, even with its partner’s support, is slightly short of a majority in both houses.

“We are setting sail under rough and difficult conditions. But I will never give up," Takaichi said at her inaugural press conference Tuesday night.

In Takaichi and the Japan Innovation Party, analysts say the U.S. will find an administration more open to boosting military spending than some previous Japanese governments. The U.S. has been pressuring allies in Asia and Europe to increase defense spending to counter threats from rivals including China and Russia.

Takaichi is an acolyte of the late Shinzo Abe, a former prime minister and Trump ally.

She said she would tell Trump that “Japan on its own will strongly enhance its defense forces" while maintaining its alliance with the U.S. as the cornerstone of its security. Tokyo, she said, “is an indispensable partner for America’s China strategy and its Indo-Pacific strategy."

The Pentagon has said it wants U.S. allies to spend as much as 5% of annual gross domestic product on defense, a figure more than double the Japanese government’s current goal of lifting spending to 2% of GDP by the fiscal year ending March 2028. Japan spent around $55 billion on defense in 2024, or about 1.4% of GDP, according to the Stockholm International Peace Research Institute. Takaichi was asked about her spending target at the press conference but didn’t directly answer.

“The Japanese fully expect pressure from the Trump administration for them to spend more money on defense," said David Boling, director of Japan and Asia trade at Eurasia Group, a consulting firm. “Eventually, the heat is going to come down on this."

Takaichi, who played drums in a rock band and rode a motorcycle in her youth, was elected president of the Liberal Democratic Party earlier this month after her predecessor as both LDP leader and prime minister, Shigeru Ishiba, said he would resign.

Ishiba, who secured the trade deal with the U.S., had been under pressure to stand down after a year in his post following back-to-back election losses that cost the LDP’s ruling coalition its majority in both houses of Japan’s parliament, the Diet.

Takaichi’s victory on Tuesday wasn’t smooth sailing. Komeito, the LDP’s coalition partner for 26 years, abruptly left the partnership not long after she won the LDP presidency, which left the LDP well short of the votes needed to install Takaichi as prime minister. Komeito’s leaders said they were unhappy with her noncommittal stance on rewriting political financing rules, one of its key goals.

Sensing Takaichi’s vulnerability, opposition parties attempted to coalesce around a rival candidate for prime minister who could have beaten her in the parliamentary vote. In the end, however, Takaichi persuaded the Japan Innovation Party to back her candidacy and the opposition push fizzled amid disagreements over policy.

In choosing the conservative Takaichi as its new leader, the center-right LDP is gambling that it can improve its electoral fortunes by winning back conservative voters who have deserted the party in favor of populist right-wing upstarts such as Sanseito, which won a rash of seats in a parliamentary election in July on an anti-immigration platform.

The stock market has welcomed Takaichi’s ascendance, rising about 8% since she was elected LDP leader.

Takaichi has long been an advocate of lifting government borrowing and spending to drive growth and revitalize Japanese industries, some of which are under pressure in global markets from Chinese rivals. The Japan Innovation Party espouses free-market ideas including lower taxes and deregulation, which if implemented could further jolt the economy.

Write to Jason Douglas at jason.douglas@wsj.com