Family Law in Japan

The Constitutional and Statutory Framework

Japanese family law is codified in Book IV (Family) of the Civil Code (Minpo, Articles 725–881). Post-World War II reforms (1947) dismantled the prewar ie (household) system — a patriarchal, primogeniture-based structure — and replaced it with a framework grounded in individual dignity and equality of the sexes, as mandated by Article 24 of the Constitution. Article 24 provides that “marriage shall be based only on the mutual consent of both sexes” and that laws must be enacted “from the standpoint of individual dignity and the essential equality of the sexes.” The Family Court (Katei Saibansho), established in 1948, exercises jurisdiction over family matters, operating with a combination of judicial and quasi-therapeutic functions and employing family court probation officers (katei saibansho chosakan) to investigate and mediate.

Marriage: Formation and Validity

A valid marriage requires compliance with Article 739: the parties must submit a notification of marriage (kon’in todoke) to the municipal registrar. Marriage is effective upon acceptance; a religious ceremony without registration has no legal effect. Substantive requirements include: (i) mutual consent; (ii) minimum age 18 for both parties (following the 2022 reform); (iii) no existing valid marriage; (iv) no prohibited degrees (lineal relatives, siblings, and collateral relatives within three degrees); and (v) compliance with the post-divorce waiting period for women (six months, Article 733 — a provision long criticized as discriminatory).

The prohibition on same-sex marriage, derived from Article 731’s requirement of “mutual consent of both sexes,” has been the subject of constitutional challenges across multiple district courts. In the Sapporo District Court decision (March 17, 2021), the court held the prohibition violates Articles 14(1) (equality) and 24(2) of the Constitution, but declined to order legislative amendment. Subsequent decisions by the Tokyo District Court (2022), the Osaka District Court (2022, upholding constitutionality), and others have produced a judicial split expected to reach the Supreme Court. As of 2026, same-sex marriage remains unavailable, though municipalities increasingly issue partnership oath certificates with limited legal effect (hospital visitation, public housing).

The marital surname system (Article 750) requires spouses to share a single surname. In practice, 95% of couples choose the husband’s surname. The requirement was upheld by the Supreme Court in Decision of December 16, 2015 and reaffirmed on June 23, 2021, with the Court holding any reform to be a matter of legislative policy. A substantial body of academic opinion regards the requirement as incompatible with the Convention on the Elimination of All Forms of Discrimination Against Women.

Divorce

Japanese law recognizes four divorce forms. Mutual consent divorce (kyogi rikon, Article 763), accounting for over 85% of divorces, requires only a filed divorce notification signed by both parties with two witnesses — no court involvement. The process has been criticized for inadequate protection of weaker parties. Divorce by mediation (chotei rikon) occurs when parties submit their dispute to the Family Court’s mediation committee (a judge and two lay mediators). Mediation is mandatory before contested proceedings; a recorded agreement has the effect of mutual consent divorce. Divorce by adjudication (shimpan rikon) occurs when mediation fails and the Family Court issues an adjudication, subject to a two-week objection period. Contested divorce (saiban rikon) under Article 770 requires one of five grounds: (i) adultery; (ii) malicious abandonment; (iii) three or more years’ separation without prospect of reconciliation; (iv) serious mental illness; or (v) “any other grave cause.” The 1987 amendments introducing separation liberalized divorce, and the “other grave cause” provision has been expansively interpreted.

The property division obligation (Article 768) covers distribution of marital property, spousal support, and pension division. The theory of contribution (kyōdō ryōsan) recognizes the non-working spouse’s contribution through household labor and child-rearing. The Family Court exercises broad discretion based on marriage length, economic circumstances, and property acquisition. Spousal support (reikon bessō) under Article 768(2) is typically time-limited, aimed at economic rehabilitation rather than permanent support. Child support (yōiku ryō) follows Supreme Court guidelines considering both parents’ incomes and the child’s needs, but enforcement remains weak — non-payment is not a criminal offense, and Japan lacks centralized wage garnishment or tax interception systems.

Parental Authority and Custody

Parental authority (shin’ken, Articles 818–837) is exercised jointly during marriage. Upon divorce, the law historically vested custody in a single parent — a system criticized as a cause of international parental child abduction and inconsistent with the child’s best interests. The 2024 Civil Code reform, effective April 1, 2026, introduced joint custody (kyōdō shin’ken) as an option. Under amended Articles 819 and 766, parents may agree on joint custody or the Family Court may order it in the child’s best interests. The reform applies only where both parents are Japanese nationals or Japan-resident; international abduction cases remain under the single-custody framework, creating tension with the Hague Convention on Child Abduction (Japan acceded in 2014).

Adoption

Japanese law recognizes ordinary adoption (futsū yōshi engumi, Articles 792–805) and special adoption (tokubetsu yōshi engumi, Articles 817-2–817-11, introduced 1987). Ordinary adoption requires consent of the adoptive parents and the child’s representatives (or the child if aged 15 or older) and Family Court approval. The child assumes the adoptive surname and acquires full inheritance rights. Special adoption severs all legal ties with biological parents and requires a judicial finding that the child’s welfare necessitates it, available only for children under six (extended to under 15 if continuously in the prospective parents’ care).

The Role of the Family Court

The Family Court (Katei Saibansho) is the central institutional actor, with jurisdiction over divorce mediation, parental authority disputes, child support, custody, property division, inheritance, juvenile delinquency, and domestic violence protection orders. The court combines adversarial and inquisitorial functions: it may investigate facts, summon witnesses, and order party examination on its own initiative. Family court probation officers (chosakan) investigate and recommend resolutions based on social welfare considerations. The court’s judicial philosophy has been described as paternalistic welfarism — prioritizing settlement, harmony, and child welfare over formal adversarial adjudication.