Adult Adoption in Japan generally refers to ordinary adoption under the Civil Code where both parties are adults. In law, an adoptive parent must have reached the age of majority, which Japan lowered from 20 to 18 on April 1, 2022, and may adopt another person as their child; the adoption is made effective by filing a notification that is accepted under the Family Register Act. Once accepted, the adopted person becomes a legal child in wedlock of the adoptive parent and is entered in the koseki, Japan’s family registry. These features make adult adoption a practical legal tool for forming kinship, for succession planning, and for unifying a household in the family register.
Reasons for Adult Adoption in Japan
Adult adoption in Japan has long been used for practical, cultural, and legal purposes. Unlike in many countries where adoption is primarily for minors, the Japanese legal system has developed adult adoption as a flexible tool to secure family succession, maintain household continuity, and create legally recognized kinship ties.
Inheritance and Succession Planning
One of the most common reasons is inheritance and succession planning. Under the Civil Code, adopted children have the same inheritance rights as biological children, which makes adult adoption a way to secure heirs when there are no biological descendants. Families, especially those with traditional businesses or estates, often adopt adult heirs to ensure that property and leadership pass smoothly. Research on Japanese family firms confirms that adopting heirs has been a widespread strategy for maintaining long-term continuity in family enterprises.
Support Obligations
Another motivation is support obligations and caregiving. Adoption creates reciprocal duties of support between adoptive parents and children under the Civil Code. Older adults sometimes adopt a trusted younger person to ensure that they will be cared for, while adoptees benefit from inheritance and legal recognition of their caregiving role.
Same Sex Couples
Finally, in recent years, same sex couples have turned to adult adoption as a way to secure legal family recognition. Since Japan does not yet recognize same sex marriage at the national level, adoption can provide inheritance rights, hospital visitation recognition, and inclusion in the family register, even though it is not equivalent to marriage and carries legal limitations .
Together, these reasons show why adult adoption remains a distinctive and widely used legal practice in Japan, blending historical continuity with modern adaptations to changing social needs.
Requirements For Adult Adoption in Japan
The Civil Code sets clear baseline requirements. Adoptive parents must have reached the age of majority (now 18), and may not adopt an ascendant or a person who is older than themselves. If a party is married, additional consent rules apply, as explained in the next paragraph.
If the adoptive parent is married, the spouse’s consent is required for the adoption. If the person to be adopted is married, that person’s spouse must also consent. When adopting a minor, a married person must adopt jointly with their spouse, subject to limited statutory exceptions.
For minors, ordinary adoption requires family court permission, except where the child is a lineal descendant of the adoptive parent or of the adoptive parent’s spouse. By contrast, adult adoption does not require family court permission; it is completed by filing the proper notification and having it accepted under the Family Register Act. The Civil Code also applies the marriage‑notification provision to adoption, which is why the document must bear signatures of both parties and at least two adult witnesses.
| Requirement / Rule | Details |
|---|---|
| Age of adoptive parent | Must have reached the age of majority (18 as of April 1, 2022). Cannot adopt an ascendant or someone older than themselves. |
| Consent when adoptive parent is married | Spouse’s consent required for adoption. |
| Consent when adoptee is married | Adoptee’s spouse must also consent. |
| Adult adoption (18+) | No family court permission required. Adoption is completed by filing a notification under the Family Register Act. |
| Notification procedure | Adoption notification must include signatures of both parties and two adult witnesses. |
