The Tokyo High Court has ruled that Japan's definition of marriage as a union between a man and a woman is constitutional, concluding the last of six major high court cases brought between 2019 and 2021.
The decision, delivered on Friday, reverses a 2024 ruling by a separate Tokyo panel that sought to redefine marriage to include same-sex couples.
Presiding Judge Ayumi Higashi stated that Japan's historic definition of marriage remains reasonable under existing law, noting that any change "should first be deliberated in parliament." The court dismissed the plaintiffs' claims for damages.
The decision affirmed that male-female marriage serves an established social purpose in Japan. As reported by Japan Today, the ruling held that the historic marriage system is "useful in preparing an environment for raising children," and that interpreting "husband and wife" as referring to a man and a woman remains consistent with Article 24 of the Constitution.
The court said the freedom of marriage guaranteed under that article does not apply to same-sex couples.
Five earlier high court rulings -- in Sapporo, Tokyo, Nagoya, Osaka and Fukuoka -- had concluded that the the existing law that upholds a straightforward definition marriage violated constitutional guarantees, though all rejected compensation claims.
Now that all regional rulings have been issued, the consolidated cases are expected to move to the Supreme Court, with a unified decision anticipated next year.
Eight plaintiffs in their 40s to 60s sought one million yen each (approximately AU$8,000), arguing that marriage law provisions excluding same-sex couples breach constitutional protections under Articles 14 and 24.
The government countered that Japan's Constitution, ratified in 1946, defines marriage as between a man and a woman, citing Article 24's opening line: "Marriage shall be based only on the mutual consent of both sexes." The court agreed with that position.
Japan is the only G7 country that continues to uphold the longstanding definition of marriage.
It is also the only country worldwide that requires married couples to share a surname, reflecting Japan's historical emphasis on family unity and household cohesion.
The Stanford Japan Barometer (SJB), a large-scale public opinion survey, reported in 2024 that 47.2% of the Japanese public was either "very much in favour" or "somewhat in favour" of legalising same-sex "marriage".
Meanwhile, 36.9% said they were neutral and 15.8% expressed opposition, revealing far less support for redefining marriage than in most Western nations, even as lawmakers face increased pressure from activists.
The Tokyo High Court noted that some legal effects of marriage can be approximated through private contracts and that individuals may marry if they change their legal sex.
Its ruling emphasised that decisions about the structure of marriage fall primarily to parliament.
Japan's commitment to marriage follows the prevailing pattern in Asia, where most countries maintain the institution's historic definition, and same-sex "marriage" is recognised only in Taiwan, Thailand and Nepal.
Last month, noted conservative Sanae Takaichi became Japan's first female prime minister after winning the leadership of the Liberal Democratic Party, Japan's ruling party, as debates over marriage and family continue.
On the other side of the Pacific, recent polling suggests a resurgence of traditional views on marriage in the United States.
A recent Economist/YouGov survey found that only 54% of Americans think same-sex "marriage" should be legal, compared with Gallup's finding of 70% support in 2021.