Same-sex marriage in Japan has no legal recognition at the national level, making Japan the only G7 country without either marriage equality or a national civil union system. Municipal partnership certificates now cover more than 90 percent of the population, but they are administrative documents, not marriage. The question is live at the top: between 2024 and 2025, four of five high courts found the ban unconstitutional, and in March 2026 the Supreme Court sent six related cases to its Grand Bench. A ruling is expected as early as fiscal year 2026, which runs through March 2027.
Why the Ban Exists: Article 24 and “Both Sexes”
Article 24 of the Japanese Constitution states that “marriage shall be based only on the mutual consent of both sexes and it shall be maintained through mutual cooperation with the equal rights of husband and wife as a basis.” A second paragraph requires that marriage and family laws be enacted “from the standpoint of individual dignity and the essential equality of the sexes.”1The House of Representatives, Japan. The Constitution of Japan
The phrase “both sexes” is doing all the work. The government reads it as limiting marriage to a man and a woman. Critics read it as a postwar guarantee that both parties must freely consent, written to dismantle the prewar system in which household heads chose their children’s spouses. On that reading, Article 24 protects individual autonomy rather than defining who may marry. This textual disagreement is the core legal question the Supreme Court now has to answer.
Why You Cannot Register a Same-Sex Marriage
Marriage in Japan is a registration, not a ceremony. A marriage becomes legally valid only when a couple files a notification with their local government office under the Family Registration Act, which then updates the koseki, Japan’s family register.2Japanese Law Translation. Civil Code – Chapter II Marriage Every Japanese citizen belongs to a koseki that records births, deaths, marriages, adoptions, and divorces. On marriage, a couple either creates a new shared register or one joins the other’s, and both adopt a common surname.
The Civil Code uses gendered language throughout. Article 750 refers to “a husband and wife” choosing a shared surname. Municipal offices will not process a marriage notification from two people of the same sex, and without a koseki entry the couple remains legally single no matter how long they have lived together. Every national benefit, tax rule, and legal protection tied to marital status runs through this register, and same-sex couples are locked out of all of it.
Municipal Partnership Certificates
Local governments began building their own systems in 2015. Shibuya and Setagaya, two wards within Tokyo, were the first to introduce partnership oath systems that let same-sex couples declare their commitment before a municipal official. As of mid-2025, more than 530 municipalities had adopted similar programs, covering over 90 percent of Japan’s population, and more than 9,800 couples had received certificates. Some major private companies, including Dai-ichi Life Insurance and Nippon Life Insurance, accept the certificates when a same-sex partner is being named as a life insurance beneficiary.3Nippon.com. LGBT Acceptance Spreads from Shibuya Employers increasingly use them to extend family leave and spousal benefits.
What they are not: marriage. A partnership certificate carries no weight under national law and does not change the koseki. It will not help with your national tax return, grant inheritance rights, affect pension entitlements, or support a residence visa application for a foreign partner. It can help with hospital visitation and applications for municipal services within the issuing municipality. That is the ceiling.
What Same-Sex Couples Lose Without Legal Marriage
Inheritance and Taxes
This is where the gap hurts most. Under the Civil Code, intestate inheritance rights belong exclusively to a surviving spouse, children, parents, and siblings.4Japanese Law Translation. Civil Code of Japan – Chapter II Marriage A same-sex partner is none of these. If a partner dies without a will naming the other, the surviving partner has no legal claim to the estate even after decades together. Assets flow to the deceased’s blood relatives.
A will helps, but the tax treatment is still harsh. Japan’s spousal inheritance tax credit lets a surviving legal spouse deduct either their statutory share or ¥160 million, whichever is larger, from the tax calculation.5Ministry of Finance, Japan. Structure of Inheritance Tax A same-sex partner inheriting by will gets none of that credit. They also do not count toward the statutory-heir basic exemption of ¥30 million plus ¥6 million per statutory heir, so the whole estate is taxed as though they do not exist. The annual gift tax exemption of ¥1.1 million per recipient applies regardless of relationship, but it is a small channel for transferring meaningful assets.
Healthcare and Medical Decisions
Japanese hospitals generally restrict medical decision-making to legally recognized family members. Because a same-sex partner is not on the koseki as a spouse, they can be excluded during emergencies. A partnership certificate may help with visitation in the issuing municipality, but it does not create a binding legal right to make medical decisions for an incapacitated partner.
Parenting
Japanese law does not permit joint adoption by same-sex couples, nor second-parent adoption of a partner’s biological child. Osaka in 2017 became the first city to recognize a same-sex couple as foster parents, but that remains uncommon. Without a legal parental relationship, the non-biological parent has no automatic custody rights if the biological parent dies or the couple separates.
Immigration
Japan does not issue spousal visas to same-sex partners of Japanese citizens. A 2013 internal memo from the Ministry of Justice created a narrow exception: if both partners are foreign nationals and their same-sex marriage is legally registered abroad, the accompanying partner may apply for a “designated activities” visa. The exception does not reach binational couples where one partner is Japanese.
Adult Adoption as a Workaround
Some same-sex couples use adult adoption as a partial substitute. Japan’s Civil Code allows one adult to adopt another, a mechanism historically used for business succession. Once the adoption is registered on the koseki, the two are legally parent and child. They share a surname, gain mutual inheritance rights, and can make medical decisions for each other as family.
The costs are real. The legal relationship is parent-child, not partnership, and if Japan eventually legalizes same-sex marriage a couple joined through adoption would need to dissolve the adoption before they could marry. Some couples instead use notarized agreements covering inheritance, medical decisions, and shared property, though private contracts are harder to enforce than a koseki-based family tie.
Where the Courts Stand
Beginning in 2019, same-sex couples filed coordinated lawsuits in five cities arguing that the marriage ban violates the constitution. The decisions have moved steadily, though not uniformly, toward recognizing marriage equality.
District Courts
The Sapporo District Court ruled first in March 2021, holding that denying same-sex couples all legal benefits of marriage violates Article 14’s equality guarantee.6Lawyers for LGBT and Allies Network. Sapporo District Court Marriage Decision Translation It accepted that Article 24 was written with opposite-sex couples in mind but found that providing no legal framework at all for same-sex relationships lacked any rational basis. The Osaka District Court in June 2022 went the other way, upholding the ban on the ground that wills and contracts give same-sex couples sufficient alternatives. The Tokyo District Court later that year described the Diet’s failure to create any system as a “state of unconstitutionality” without striking the statutes down.
High Courts
The high courts have been more decisive. The Sapporo High Court ruled in March 2024 that the ban violates both Article 14 and Article 24, holding that Article 24 “guarantees freedom of sexual orientation and the right to marriage between individuals of the same sex” and that current restrictions “exceed the legislative discretion of the Diet.”7Lawyers for LGBT and Allies Network. Sapporo High Court Decision Translation The Fukuoka High Court followed in December 2024, finding a violation of the right to pursue happiness. The Nagoya High Court reached the same conclusion in March 2025, calling the exclusion of same-sex couples from legal marriage “unlawful discrimination.” An earlier Tokyo High Court panel in 2024 also found the ban unconstitutional. The exception came in November 2025, when a different Tokyo High Court panel ruled that the ban violates neither Article 14 nor Article 24.
Supreme Court
On March 25, 2026, the Supreme Court’s Third Petty Bench forwarded six same-sex marriage cases to the Grand Bench, the full 15-justice panel that handles constitutional questions. This will be the first time the Supreme Court interprets the constitutional provisions on marriage as applied to same-sex couples. A ruling is expected as early as fiscal year 2026, through March 2027. Public support for marriage equality stood at roughly 72 percent as of 2025, and the lower courts have, with one exception, found the ban unjustifiable. Whether the Grand Bench follows that trajectory or defers to the Diet will determine Japan’s direction on marriage recognition.