JapanHow to use adult guardianship system?
To use Japan’s adult guardianship system, a family member or interested party must file a petition with the family court requesting the appointment of a guardian for someone who lacks sufficient judgment capacity due to dementia, intellectual disability, or mental illness.
What the Law Says
Japan’s adult guardianship system is established under the Civil Code and the Act on Support for Persons with Disabilities. It provides legal support for adults aged 15 or older who cannot make sound decisions about their personal or financial affairs due to cognitive impairment.
The system has three levels: guardianship (for those with severely impaired judgment), curatorship (for those with significantly impaired judgment), and assistance (for those with mildly impaired judgment). Each level grants different powers to the appointed supporter.
A guardian may manage property, consent to medical treatment, and represent the person in legal matters — but only within the scope authorized by the family court.
Only the family court can appoint a guardian, curator, or assistant after reviewing medical evidence and hearing from the person concerned (if possible) and interested parties.
Statutory TextAn adult who, due to a mental disorder, is unable to understand matters concerning his/her person or property, may be placed under guardianship.
— Civil Code, s. 839 — Guardianship
Statutory TextThe family court shall appoint a guardian upon petition by the person concerned, a relative within the fourth degree of kinship, a spouse, or a public prosecutor.
— Civil Code, s. 840 — Appointment of Guardian
Statutory TextA guardian shall act in the best interests of the person under guardianship and shall respect his/her wishes and dignity to the greatest extent possible.
— Act on Support for Persons with Disabilities, s. 5 — Duties of Supporters
What to Do
Confirm the person is aged 15 or older and shows signs of impaired judgment (e.g., dementia, intellectual disability, severe mental illness).
Obtain a medical diagnosis from a qualified physician confirming the condition and its impact on decision-making.
File a petition at the competent Family Court (usually where the person resides) using official forms and supporting documents.
Attend the court hearing; the court may interview the person and hear from family members or experts.
If approved, the court issues an order appointing the guardian and specifying their authority and reporting duties.
Sources
Not legal advice. This article is general information based on publicly available sources, written for educational purposes. Laws change and individual situations vary. Consult a licensed attorney in your jurisdiction before acting on anything you read here. Last reviewed: 2026-06-08.