Domestic Partnerships and the Future of Marriage Law
Domestic partnership Japan covers couples who live as spouses without filing a marriage registration, and the gap between that life and full legal marriage is wider than many newcomers expect.12 The difference decides visa eligibility, default inheritance, and custody starting points, so this article maps each layer before you rely on it.
Procedures, fees, and requirements can change. Confirm current details at the Ministry of Justice family register guidance and the Immigration Services Agency site. This article is general information, not legal, tax, or immigration advice; for your specific case, consult a licensed family-law attorney (bengoshi), or a gyoseishoshi for document and filing reads.
Overview
A marriage becomes legally valid in Japan only when a municipal office accepts the couple's marriage notification.1 A 内縁 (naien, "de facto marriage") or 事実婚 (jijitsukon, "factual marriage without registration") describes cohabitation with spousal intent but without that accepted filing.2
An estimated 2 to 3 percent of adults live in such unions by simple calculation from surveys, including a 2022 Cabinet Office survey in which 3.3 percent of 10,906 respondents chose common-law marriage (as of 2025-03-12).2 The rest of this article keeps three layers apart: de facto effects recognized case by case, municipal certificates honored locally, and national marriage status granted only by registration.
The terms below recur throughout this article:
| Japanese term | Romaji | English gloss |
|---|---|---|
| 内縁 | naien | De facto marriage without registration |
| 事実婚 | jijitsukon | Factual marriage without registration |
| 婚姻届 | konin todoke | Marriage registration form |
| 戸籍 | koseki | Family register, citizens only |
| パートナーシップ宣誓制度 | pātonāshippu sensei seido | Partnership oath system, municipal certificate scheme |
| 選択的夫婦別姓 | sentakuteki fūfu bessei | Selective separate surnames reform proposal |
De Facto Unions Without Registration
A de facto union means the couple lives with genuine spousal intent but never completes the accepted notification that Article 739 requires.12 Japan grants no automatic spousal status on that basis. Courts extend protection case by case rather than as blanket marital equivalence.12
A foreign common-law finding does not transfer as spousal status inside Japan. Domestic registration at a municipal office is the trigger for Japan-domestic spousal effects, so confirm with your local office rather than assuming your home-country status carries over.13
What counts as a de facto union
Cohabitation plus mutual intent to live as spouses is the substance courts look for, while the accepted filing is the form the Civil Code requires.12 Without that form, the union stays outside the statutory marriage framework even when daily life looks identical to a registered marriage.
A ceremony, shared lease, or joint bank account shows intent but creates no marriage status. Only acceptance of the notification at the counter creates it.1
Where limited recognition already applies
Some protections do reach de facto spouses in specific statutes. Wrongful termination of a de facto union can support damages, yet no spousal inheritance share follows from the same relationship.12
In social security and related benefit contexts, de facto spouses may in certain circumstances be treated like legal spouses, but the answer depends on each statute (as of 2026-09-08; confirm current figures with the administering agency).2 Practitioner sources describe uneven coverage across pension and insurance line items, but figures are inconsistently reported, so treat any specific benefit as scheme specific until you check that scheme.
The Supreme Court has confirmed one such scheme specific extension. A same-sex partner can qualify as a person in a de facto marital relationship for crime victim survivor benefits, with the court remanding for fact finding on cohabitation and cooperation.4
What Formal Marriage Alone Changes
Registration alone moves a couple into the national spousal framework. The table below summarizes the boundary; details follow in each subsection.
| Layer | Spousal defaults | As of | Source |
|---|---|---|---|
| Registered marriage | Full defaults apply | 2026-09-08 | 1 |
| De facto union | Case by case only, no spousal share | 2026-09-08 | 12 |
| Partnership certificate | Local help only, no national defaults | 2026-08-01 | 5 |
These contrasts reflect the current statute and case position (as of 2026-09-08; confirm current figures with the Ministry of Justice).
Visa eligibility reserved to registered spouses
Spouse or Child of Japanese National status covers the husband or wife of a Japanese national.6 Available periods of stay are 5 years, 3 years, 1 year, or 6 months, set case by case (as of 2026-09-08; confirm current figures with the Immigration Services Agency).6
A de facto partner does not qualify as a spouse for this status (as of 2026-09-08).6 Only a registered spouse falls in the covered category. The same spouse only logic appears abroad as well: common-law partners are generally not treated as spouses for family accompaniment in major destinations including the United States.2
Do not plan a move or a job resignation around a future spouse filing unless you will actually register. Immigration outcomes still require a registered marriage or a separate qualifying status.6
Inheritance defaults, tax treatment, and property division
The Civil Code reserves the spousal inheritance share to a legal spouse, with statutory shares fixed by the inheritance provisions.1 A de facto partner has no spousal inheritance right, so leaving property to the partner requires a will or bequest.12
Even when a de facto partner inherits through a will, the partner stays ineligible for the spousal inheritance tax reduction (as of 2025-03-12).2 Common-law spouses are likewise ineligible for the spousal deduction (as of 2025-03-12).2 A will moves property; it does not move the tax status.
Divorce property division attaches to termination of a registered marriage, not to dissolution of a de facto union under the same provision.1 De facto separation disputes fall back on general civil rules rather than marital presumptions.
Custody, divorce framework, and koseki recording
Marriage takes effect upon acceptance of the notification, and married couples must use one shared surname at registration.17 The Japanese spouse's 戸籍 (koseki, "family register") records the marriage. A foreign spouse receives no independent koseki entry.3
Partnership certificates do not alter koseki status (as of 2026-08-01).5 Only the accepted marriage notification rewrites the register.
In common-law unions the mother in principle holds sole custody of children.2 A biological father outside marriage establishes the legal parent child link through acknowledgement, not automatically.1 Parental authority after acknowledgement or divorce then follows the Civil Code determination rules rather than automatic joint custody.1
Municipal Partnership Certificates
A partnership certificate is a local pledge document, not a national marriage. It can ease daily life where the issuer's services accept it, but it creates no national spousal rights.
Couples use this map to pick the right layer: registration for national effects, a certificate for local help where available, or private planning where neither fits (as of 2026-08-01).5
Who can apply and where
As of 2026-08-01, 566 municipalities and 31 of 47 prefectures operate a partnership oath or certification system, covering about 93.79 percent of the population (as of 2026-08-01).5 The systems began with Shibuya Ward in 2015 and spread to wards, cities, and prefectures including Tokyo, Osaka, Sapporo, and Fukuoka (as of 2026-08-01).58
Most systems target same-sex couples. Some jurisdictions extend to opposite-sex common-law couples, with Tokyo as the first prefecture level jurisdiction to do so (as of 2026-08-01).5 Ward offices vary in how they handle eligibility and evidence, so confirm with your local office before you apply.
What a certificate helps with day to day
Certificates may help with municipal housing applications, hospital visitation, and consent-adjacent procedures, alongside encouragement to local employers and landlords.85 Tokyo and other large issuers publish guides describing these local uses.
Coverage is local and voluntary. A phone call before you move or book care saves more time than the certificate alone.5
What a certificate does not change
The system is not legally binding at national level. Hospitals and landlords carry no legal obligation to honor a certificate even when presented.5
A certificate creates no koseki entry, no spousal inheritance share, no spousal tax treatment, and no spouse visa eligibility.165 Municipal offices still reject same-sex marriage filings under the current reading of the Civil Code and Family Register Act.81
Children and Inheritance Planning Without Marriage
Unmarried parents can plan around parts of the gap, but planning cannot replicate registration. Treat wills and agreements as partial tools with known ceilings.
Custody and acknowledgement of children born outside marriage
A child born outside registered marriage is registered on the mother's koseki.12 The father enters the legal picture through acknowledgement under the affiliation provisions, not automatically.1
Acknowledgement is the step that creates the link the custody decision then builds on. Start it early rather than assuming biology alone suffices.1
Wills and agreements as partial workarounds
A will can direct property to a de facto partner, but it cannot confer the spousal tax reduction or spousal share defaults.12 Private agreements on shared property, medical decision intent, and beneficiary designations are harder to enforce and less universally recognized than koseki based family status.8
Medical institutions retain discretion on whether a de facto partner may consent to treatment (as of 2025-03-12).2 A written intent statement may help staff understand your wishes, but it does not bind every institution the way a registered spouse's authority does.
Legislative Watch
Reform status below is date-stamped because it moves with Diet sessions and court calendars. Headlines grant no filing rights until a bill passes or a court decides.
Selective couple surnames
Current law requires one shared surname at marriage. In practice about 94.1 percent of couples in Reiwa 6 chose the husband's surname (as of 2026-09-08; confirm current figures with the Ministry of Justice).7
The selective separate surname proposal would let couples opt to retain premarital surnames while keeping all other marital rights and duties identical (as of 2026-09-08).7 A separate-surname couple would still be a registered legal couple, distinct from an unregistered de facto couple.7
The 1996 Legislative Council recommended introduction, but amendment bills prepared in 1996 and 2010 were never submitted to the Diet.7 The Supreme Court Grand Bench upheld the single-surname rule as constitutional in 2015 and 2021, while stating the design is for the Diet to decide.7
Opposition bills were deliberated in the House of Representatives Committee on Judicial Affairs in June 2025 with no vote before the session ended 2025-06-22 (as of 2025-07-01).9 For the February 8 House of Representatives election, the LDP pledge backed legalizing maiden name use as a common name rather than adopting optional separate surnames, with a related bill planned for the 2026 ordinary Diet session (as of 2026-01-28).9
Surname pressure is the main stated driver of non-registration. In a May 2024 survey of 111 people in common-law marriages, 86 percent said they had not registered because they did not want to change a surname, and 92 percent said they would register if a selective surname system were legalized (as of 2025-03-12).2
Same-sex marriage recognition
National law does not register same-sex marriage. Japan remains the only G7 member without national same-sex marriage or civil union status (as of 2026-03-26).108
Five high courts in Sapporo, Tokyo, Fukuoka, Nagoya, and Osaka ruled the excluding provisions unconstitutional, citing equality, individual dignity, pursuit of happiness, or freedom of marriage depending on the court (as of 2026-03-26).10 One Tokyo High Court panel in November 2025 ruled the provisions constitutional, reading a married couple as a man and a woman in legal terms (as of 2026-03-26).10
On 2026-03-25 the Supreme Court Third Petty Bench sent six related damages suits to the 15-justice Grand Bench for a unified constitutional ruling, expected as early as fiscal 2026 (as of 2026-03-26).10 Damages claims were rejected in all six cases even where provisions were found unconstitutional (as of 2026-03-26).10
Pending litigation grants no filing rights at the counter today. No statute change has reshaped the marriage provisions as of the referral date (as of 2026-03-26).10
Good to know
A foreign common-law status does not transfer on arrival
Some couples arrive assuming a home-country common-law finding works as a spouse status in Japan. It does not. Japan-domestic spousal effects trigger on accepted domestic registration, so file domestically or hold a separate qualifying status before relying on spousal treatment.13
A partnership certificate creates no visa path
Certificate holders sometimes assume immigration will recognize the paper. Immigration does not. Spouse statuses require a registered spouse, so a certificate alone supports neither a new spouse filing nor a change into a spouse status.65
Staying unregistered to keep surnames forfeits spousal defaults
Keeping separate surnames by not registering preserves identity but surrenders the spousal inheritance share, the spousal tax reduction, and the spousal deduction. A will replaces only the property direction, not the tax treatment, so price the trade before choosing it.12
Pending reform grants no rights until enacted or decided
Surname bills and the Grand Bench referral move slowly and can stall between sessions. Check the as of dates in the Legislative Watch section and confirm with the municipal counter handling your filing, since only enacted law or a decided ruling changes what staff can accept.109
See also
- Same-Sex Marriage Status in Japan
- Marriage to a Japanese National
- Marriage Between Two Foreigners in Japan
- Choosing Surnames in International Marriages
- Spouse Visa Application After Marriage Registration
- Birth Registration and the 14-Day Rule