[Answer]
Article 5 of the Nationality Law says that a
person wishing to obtain Japanese nationality by “naturalization” needs to
fulfill the following eligibility requirements:
1) a person must have
domiciled in Japan for five or more consecutive years;
2) a person must be 20
years of age or over and of sound mind according to the law of his or her
country of origin;
3) a person must be of
upright character;
4) a person must be able
to secure a livelihood by his or her own property or ability, or those of a
spouse or other relatives with whom the person lives and shares living
expenses;
5) a person must be
stateless or be prepared to give up his or her original nationality on becoming
a naturalized Japanese citizen;
6) a person must, since
the enactment of the Constitution, never have plotted or advocated or formed or
belonged to a political party or other organization which has plotted or
advocated the overthrow of the constitution of the existing government.
You can apply for naturalization at the appropriate Legal
Affairs Bureau that serves your area by submitting required documents. These
requirements are very dependent on your marital or biological relationship with
Japanese nationals. If you are married to a Japanese or if you were born in
Japan, for example, requirements for naturalization are relaxed.
Once your naturalization is granted, your new family
registry is made. You can consult with and apply at a legal affairs office of
your area. Documentary examination based on the submitted documents is followed
by substantive examination.