The Separate Property System in Japanese Family Law

Introduction

Japanese family law adopts a separate property system (zaisan bengosaku) for married couples, codified in Book IV of the Civil Code (Articles 762 and following). Under this system, marriage does not create a community of property between the spouses. Each spouse retains ownership of property acquired before marriage, and property acquired during marriage in the name of one spouse is presumed to be the separate property of that spouse.

This structure differs fundamentally from the community property systems found in many civil law jurisdictions (such as France, Italy, and parts of the United States), where marriage creates a common fund of assets owned jointly by the spouses. Japan’s approach reflects the individualistic conception of marriage that underpins the post-war Civil Code reform, which rejected the patriarchal household system (ie seido) of the Meiji Civil Code in favour of equal rights between spouses.

The Statutory Framework: Article 762

Article 762(1) of the Civil Code provides: “Property acquired before marriage or property acquired during marriage in the name of a spouse shall be the separate property of that spouse.” Article 762(2) establishes a presumption of co-ownership: “All property acquired during marriage not falling within paragraph (1) shall be presumed to belong to both spouses in equal shares.”

The presumption in Article 762(2) is rebuttable. A spouse who claims that an asset is separate property rather than marital property bears the burden of proving that the asset was acquired (a) before marriage, or (b) during marriage but in that spouse’s name. Where an asset is registered in both spouses’ names, it is presumed to be co-owned, and the burden shifts to the spouse asserting separate ownership.

The Contribution Theory

The most significant doctrinal development in Japanese marital property law is the contribution theory (kōken riron), which governs the division of property at divorce. Under this theory, where one spouse’s separate property has increased in value during the marriage because of the other spouse’s contributions — whether direct (financial) or indirect (domestic labour, child-rearing, support) — the contributing spouse is entitled to a share of the increased value.

The contribution theory operates in the context of property division (zaisan bun’yō) upon divorce, which is governed not by Article 762 but by Article 768 of the Civil Code and Article 4 of the Family Law Miscellaneous Provisions (Kazoku Hō Tekiyō Hō). The court exercises broad discretion in ordering property division, taking into account all relevant circumstances, including the length of the marriage, the contributions of each spouse, and the needs of the parties.

The Family Home Cases

The family home (kyōdō jūtaku) has been the subject of extensive litigation. Typically, the family home is registered in the name of the husband alone (reflecting traditional patterns of property ownership), but the wife’s contributions to the acquisition and maintenance of the home — through domestic labour, child-rearing, and often part-time employment — give rise to a claim for a share of its value upon divorce.

Japanese courts approach the family home through the lens of the contribution theory. Where the wife’s indirect contributions are established, the court may order the husband to transfer a share of the home to the wife or to compensate her for her share in monetary terms. The courts have developed standardised formulas for calculating the wife’s contribution, often applying a 30% to 50% contribution ratio depending on the length of the marriage and the specific circumstances of the case.

Division of Pension Assets

The division of pension assets at divorce has become a central issue in Japanese family law. Prior to the 2007 amendment, pension assets were generally treated as the separate property of the employee spouse, and the non-employee spouse had no claim to a share. The 2007 amendment to the Civil Code introduced a framework for the division of public pension rights, allowing the non-employee spouse to claim a share of the employee spouse’s old-age pension (rōrei nenkin) accumulated during the marriage.

The “three-part division” approach allocates pension assets based on the ratio of the marriage period to the total contribution period. The court may order the pension authority to divide the pension payments between the spouses, with the non-employee spouse receiving a share proportional to the contribution made during the marriage.

The division of private pension assets (corporate pensions, individual retirement accounts) is governed by the general principles of property division under Article 768. Courts may order the employee spouse to compensate the non-employee spouse for the value of the pension rights accumulated during the marriage, calculated according to the contribution theory.

The Burden of Proof

The allocation of the burden of proof in establishing separate vs. marital property is of practical importance. A spouse who claims that an asset is separate property must prove: (a) that the asset was acquired before marriage, or (b) that the asset was acquired during marriage in that spouse’s name. Where the spouse discharges this burden, the asset is presumptively separate property, but the other spouse may argue that the separate property has been transformed into marital property by virtue of the other spouse’s contributions, or that the increase in the value of the separate property during the marriage should be shared.

In practice, difficulties of proof arise where assets have been commingled — for example, where funds from separate property accounts have been used to acquire assets during the marriage, or where the proceeds of sale of separate property have been reinvested in jointly-owned assets. The courts apply a tracing approach, requiring the spouse asserting separate property to trace the asset to its source.

The Impact of the Shared Surname System

Japan’s shared surname system — under which married couples are required to adopt the same surname (Article 750 CC) — has indirect effects on property ownership. In the overwhelming majority of cases, the wife adopts the husband’s surname upon marriage. This practice, combined with traditional gender roles that assign primary responsibility for domestic labour and child-rearing to women, has historically placed wives in a structurally weaker position with respect to property accumulation.

The separate property system, combined with the shared surname practice, has been criticised for perpetuating economic inequality between spouses. The contribution theory and the court’s broad discretion in property division at divorce represent attempts to remedy this inequality, but the effectiveness of these remedies depends on the willingness of courts to recognise the value of indirect contributions and on the availability of information about the husband’s assets.

Conclusion

The separate property system of Japanese family law reflects a formal commitment to spousal equality in property ownership, but its practical operation has required significant judicial intervention to prevent the system from producing inequitable results at divorce. The contribution theory, the division of pension assets, and the court’s broad discretion in property division represent the principal mechanisms through which Japanese law addresses the economic consequences of divorce. The continuing evolution of these mechanisms reflects the ongoing struggle to achieve substantive equality between spouses within a formal separate property framework.