The 'Uji' (Family Name) System in Japan: Legal Principles and Current Debates on Separate Surnames

Japanese Attorney at Law - Bengoshi L.L.

29 May 2025 • 9 min read

The uji (氏), or family name, is a fundamental component of personal identity and legal status in Japan, deeply intertwined with the nation's unique family register system known as the koseki (戸籍). Unlike many Western countries where spouses commonly retain their pre-marital surnames or have various options for combining them, Japanese law, under Article 750 of the Civil Code, mandates that a married couple must adopt a single, common surname. This principle, along with the rules governing children's surnames and the procedures for name changes, forms a distinctive legal framework that has significant social implications and has been the subject of intense contemporary debate, particularly concerning the option for spouses to maintain separate surnames.

I. The Cornerstone: The Principle of a Common Surname for Married Couples (夫婦同氏の原則 - Fūfu Dōshi no Gensoku)

Article 750 of the Japanese Civil Code stipulates: "A husband and wife shall adopt the surname of the husband or wife in accordance with that which is decided at the time of marriage." This is the legal foundation of the "principle of a common surname for husband and wife" (fūfu dōshi no gensoku).

A. The Legal Mandate and Overwhelming Practice

Upon marriage, a couple must choose to use either the husband's pre-marital surname or the wife's pre-marital surname as their new, shared family name. This chosen surname is then registered in their koseki. While the law is gender-neutral in allowing either spouse's surname to be chosen, societal convention overwhelmingly results in couples adopting the husband's surname. Statistics consistently show that over 95% (often cited as around 98%) of Japanese couples make this choice.

This practice has profound implications, especially for women, who are far more likely to change their surname upon marriage. This can lead to various practical inconveniences and a sense of discontinuity in professional and personal identity, such as needing to update official documents, bank accounts, professional licenses, and publications, and re-establishing their identity under a new name.

B. The Intense Debate on Selective Separate Surnames (選択的夫婦別姓 - Sentaku-teki Fūfu Bessei-sei)

The mandatory common surname system has been a focal point of legal and social debate in Japan for decades, with strong arguments being made for the introduction of a "selective separate surname system." This would allow spouses the option to retain their respective pre-marital surnames after marriage.

Historical Context of the Debate: The discussion gained significant momentum in the 1990s. In 1996, the Legislative Council of the Ministry of Justice, an influential advisory body, issued an outline proposal for Civil Code revisions that included the introduction of a selective separate surname system. This proposal, however, faced considerable opposition from conservative elements who argued it would undermine family unity and traditional values. Consequently, this part of the reform was not enacted and remains a contentious issue.
Arguments for Allowing Separate Surnames:
- Gender Equality: Proponents argue that the current system, in practice, disproportionately burdens women and is a vestige of patriarchal traditions, even if the law itself is facially neutral. Allowing separate surnames would be a step towards greater gender equality.
- Individual Identity and Professional Continuity: Many individuals, particularly women with established careers, wish to retain their pre-marital surname for reasons of personal identity and professional recognition. Changing names can disrupt professional networks and publication records.
- International Norms: A growing number of countries allow spouses to retain their surnames, and proponents point to this as an international trend towards respecting individual choice.
Arguments Against Allowing Separate Surnames:
- Family Unity: Opponents often express concerns that different surnames within a marriage could weaken the sense of family unity and cohesiveness. The common surname is seen as a symbol of the family as a unit.
- Children's Surnames and Welfare: Concerns are raised about potential confusion or negative impacts on children if their parents have different surnames, and which surname the child would take.
- Tradition and Social Order: Some argue that the common surname system is a long-standing tradition that contributes to social order and should be preserved.
Current Legal Status and Court Challenges: The mandatory common surname system remains law. There have been several legal challenges to the constitutionality of Article 750, arguing that it violates constitutional guarantees of equality under the law, freedom of marriage, and individual dignity. In a landmark decision on December 16, 2015 (最(大法廷)判平成27年12月16日), the Supreme Court upheld the constitutionality of Article 750, stating that while the common surname system does impose certain restrictions, it is not irrational from the legislature's standpoint, considering the surname's function in identifying individuals within a family. However, the Court also acknowledged the ongoing societal debate and suggested that the matter is primarily one for legislative policy. Subsequent challenges have also been largely unsuccessful at the Supreme Court level, though some lower court rulings have found the law unconstitutional in specific contexts, highlighting the continuing legal tension.
Public Opinion and Political Landscape: Public opinion on this issue is divided, though polls have shown increasing support for allowing selective separate surnames, particularly among younger generations and women. The issue remains politically sensitive, with differing views across political parties.

C. Surname After Dissolution of Marriage or Death of a Spouse

Divorce: Upon divorce, a spouse who changed their surname at the time of marriage automatically reverts to their pre-marital surname (Article 767, Paragraph 1, Civil Code).
Option to Retain Marital Surname (Kon'in-shi Zokushō - 婚姻氏続称): However, to mitigate inconvenience, Article 767, Paragraph 2 allows the spouse who reverted to their former surname to opt to continue using the surname they used during the marriage. This choice must be made by filing a notification within three months of the date of divorce. This is a widely used provision.
Death of a Spouse: If a marriage is dissolved by the death of one spouse, the surviving spouse's surname does not automatically change. They continue to use the marital surname. However, if the surviving spouse wishes to revert to their pre-marital surname, they can do so by filing a notification with the municipal office (Article 751, Paragraph 1).

II. The Child's Surname (子の氏 - Ko no Uji): Adherence to Parental Surname (Article 790)

The determination of a child's surname is guided by the "principle of parent-child surname conformity" (oyako dōshi no gensoku), meaning a child generally takes the surname of their parents as registered in the same koseki.

A. Marital Children (Chakushutsushi - 嫡出子)

A child born to legally married parents (a marital child) takes the common surname adopted by the parents at the time of marriage (Article 790, Paragraph 1). If the parents divorce before the child's birth, the child takes the surname the parents were using at the time of the divorce (which would have been their common marital surname).

B. Non-Marital Children (Hi-chakushutsushi - 非嫡出子)

A child born outside of a legal marriage (a non-marital child) takes their mother's surname (Article 790, Paragraph 2). If the father subsequently acknowledges the child, this does not automatically change the child's surname, though procedures exist to change it to the father's surname with Family Court permission.

C. Adopted Children (Yōshi - 養子)

An adopted child takes the surname of their adoptive parent(s) (Article 810). There's an exception if the adoptee is married and has already adopted their spouse's surname; in such cases, they continue to use their marital surname unless they were adopting their spouse's surname (in which case it naturally aligns).

III. Procedures for Changing a Child's Surname (子の氏の変更 - Ko no Uji no Henkō) (Article 791)

Circumstances can arise where a child's surname differs from that of one or both of their parents, necessitating a change for consistency or welfare.

A. When a Child's Surname Differs from a Parent's (General Rule - Article 791(1))

If a child's surname differs from that of a parent who has parental authority over them and with whom they share (or intend to share) a koseki, a petition must be filed with the Family Court for permission to change the child's surname to match that parent's. This situation commonly arises after:

Parental divorce, where one parent reverts to their pre-marital surname.
Remarriage of a parent, where that parent adopts a new marital surname.
Acknowledgment of a non-marital child by a father whose surname is different from the child's (initially the mother's).

The Family Court grants permission if it deems the change necessary for the child's benefit (子の利益のため - ko no rieki no tame). The court considers factors such as the child's age, living situation, and potential social or psychological impacts.

B. Exception: Change Without Court Permission During Parents' Marriage (Article 791(2))

A simplified procedure exists if a child's surname differs from their parents' surname because one or both parents changed their surname while they are married to each other. For instance, if a non-marital child is legitimized by the subsequent marriage of their parents, and the parents adopt a common surname different from the child's birth surname, the child's surname can be changed to match the parents' current surname by simple notification to the municipal office, without needing Family Court permission, provided both parents have parental authority.

C. Acting for Minors and Reversion Rights

If the child is under 15 years of age, their legal representative (usually the parent with parental authority seeking the change) undertakes the procedure on their behalf (Article 791, Paragraph 3).
A child whose surname was changed while they were a minor has the right to revert to their original pre-change surname by notification within one year of reaching the age of majority (currently 18) (Article 791, Paragraph 4).

D. Complexities and Judicial Discretion

Changing a child's surname can involve complex family dynamics. For example, in a case where a father, who had acknowledged his non-marital child and held parental authority, sought to change the child's surname to his own (the father was married to another woman and had children from that legal marriage), the Tokyo High Court (decision of September 19, 1985 (東京高決昭和60年9月19日家月38巻3号69頁)) denied the change. The court prioritized the child's overall welfare, considering the potential disruption and negative impact on the father's existing legal family, and suggested that maintaining the child's current surname (the mother's) was, for the time being, in the child's best interest, given the stability of the child's life with the mother despite the father having parental authority. This illustrates the court's careful balancing of interests.

IV. General Changes of Surname and Given Name (氏名の変更 - Shimei no Henkō)

Beyond changes related to parent-child relationships, Japanese law also provides for individuals to change their own surnames or given names under specific circumstances, requiring Family Court permission.

A. Changing a Surname (Article 107, Paragraph 1, Koseki Act - 戸籍法)

An individual can petition the Family Court to change their surname if there are "unavoidable reasons" (yamu o enai jiyū). This is a relatively strict standard. Examples of what might constitute unavoidable reasons include:

The surname being extremely rare, bizarre, or difficult to read or write, causing significant practical hardship or social ridicule.
Having used an alias for a very long period, such that it has become the person's primary public identifier.
For individuals seeking rehabilitation and a fresh start, such as former members of criminal organizations whose original surname is widely associated with their past.

B. Changing a Given Name (Article 107-2, Koseki Act)

Changing a given name also requires Family Court permission but under a less stringent standard of "justifiable grounds" (seitō na jiyū). This is because a given name change is considered to have less societal impact than a surname change. Examples include:

Names that are obscene, bizarre, or cause extreme embarrassment.
Names identical to infamous criminals or that invite severe ridicule.
Professional name changes, such as for artists, entertainers, or clergy adopting a religious name.
Transgender individuals seeking to align their legal name with their gender identity.

C. "Civil Code Surname" vs. "Appellative Surname"

A distinction is sometimes made between a person's "Civil Code surname" (民法上の氏 - Minpō-jō no uji), which is their fundamental legal surname based on birth or marriage, and an "appellative surname" (呼称上の氏 - koshō-jō no uji). The latter can arise, for example, when a divorced person opts to continue using their marital surname under Article 767(2). While they are publicly known by the marital surname (appellative), their Civil Code surname has reverted to their pre-marital one. This distinction can have implications for procedures like changing a child's surname to match that of such a parent, as the change is technically to align with the parent's appellative surname, not necessarily their underlying Civil Code surname.

V. Conclusion

The Japanese uji (family name) system is a deeply embedded legal and social construct, intrinsically linked to family registration (koseki) and the structure of family units. The legal mandate for married couples to share a common surname remains a defining, and highly debated, feature. While over 98% of couples choose the husband's surname, the societal and legal push for allowing selective separate surnames continues, fueled by concerns for gender equality and individual identity. The rules for determining and changing children's surnames aim to maintain consistency with parental surnames while prioritizing the child's welfare, generally requiring the oversight of the Family Court. Similarly, changes to an individual's own surname or given name are possible but are subject to judicial approval based on specific criteria of necessity or justifiability, reflecting the importance attributed to names as stable legal identifiers in Japanese society.