1. The "Capacity Requirement" and Legal "Competence"

The capacity requirement for naturalization is based on the concept of "competence to act" as defined in Japan’s Civil Code.
Competence to act refers to the legal ability to independently carry out legal actions, such as signing contracts or submitting applications.

Under the Civil Code, competence is categorized as follows:

✅ Competence Standards in Japan’s Civil Code

1. Adults (18 years and older) → Full legal competence (Can apply for naturalization independently)
2. Minors (Under 18) → Limited legal competence (Parental consent required)
3. Adults under guardianship → No legal competence (Difficult to apply for naturalization)
4. Adults under curatorship or assistance → Partially restricted competence (Naturalization may be possible depending on the case)

In naturalization applications, an applicant's legal competence to act is a key criterion for determining eligibility.

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2. Naturalization Applications for Adults (18 and Older)

✅ Adults (18 years and older) are considered to have full legal competence and can apply for naturalization independently.

However, even if an applicant meets this requirement, they should be aware of the following:

• The applicant must personally prepare and sign the required documents. (Relying too much on a representative may raise concerns.)
• The applicant must have the ability to make decisions. (For example, if the applicant has severe communication difficulties, their application may be questioned.)

➡️ As long as an applicant is 18 or older, they generally meet the capacity requirement and can proceed with the application without any special issues.

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3. Naturalization Applications for Minors (Under 18) and Parental Consent

✅ Minors under 18 are considered "persons with limited legal competence" under the Civil Code, meaning they cannot apply for naturalization independently.
➡️ Parental (or legal guardian’s) consent is required.

For example:

• If a 40-year-old foreign father applies for naturalization, his 15-year-old child can apply together with him → Allowed
• If a 15-year-old child wants to apply for naturalization alone → Not allowed (Parental consent is required)

Additionally, minors are generally not permitted to apply for naturalization unless their parent also applies.
➡️ Therefore, the standard approach is for the parent to first apply for naturalization, and then include their child in the application.

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4. The Adult Guardianship System and Naturalization Applications

Japan’s Adult Guardianship System is designed to protect individuals with dementia, intellectual disabilities, mental disorders, or other conditions that impair decision-making abilities.
There are three levels of guardianship, and each has a different impact on naturalization eligibility.

✅ Three Levels of Adult Guardianship and Their Effect on Naturalization

Type	Description	Impact on Naturalization
Adult Guardianship (成年被後見人)	The person has almost no decision-making ability, and their guardian makes legal decisions on their behalf.	Naturalization is nearly impossible
Curatorship (被保佐人)	The person has significantly impaired decision-making ability and needs a curator’s consent for important legal actions.	May be possible, depending on the case
Assistance (被補助人)	The person has partial decision-making impairment and requires an assistant’s consent for certain legal actions.	Naturalization is often possible

➡️ If an applicant has a court-appointed adult guardian, they are legally considered incompetent, making naturalization very difficult.
However, if the applicant has a curator or assistant, naturalization may still be possible, depending on their level of competence.

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5. Summary: Understanding the Capacity Requirement Based on Japan’s Civil Code

✅ The capacity requirement for naturalization is determined based on the Civil Code’s concept of "competence to act."
✅ Applicants 18 or older can apply independently.
✅ Applicants under 18 require parental consent (cannot apply alone).
✅ Applicants with a court-appointed guardian face significant challenges, while those with curators or assistants may still be eligible.

➡️ In the next article, we will explore "Special Cases and Procedures for Minors Applying for Naturalization."