From:
http://www.immigrationattorney.jp/index.php?Japanese%20Citizenship"What is Naturalization?
The act of making a person a citizen of Japan who was not born with that status. An application for citizenship is an application for Naturalization.
Non-Japanese citizens can obtain Japanese citizenship when they complete the process of naturalization.
Benefits of Becoming a Japanese Citizen
The Right to Vote in both Eligibility
Being a citizen of Japan provides many privileges. Voting in elections is one such privilege. New citizens are expected to participate in elections.
You may be elected the prime minister of Japan.
International Travel Made Easier
Permanent Residents can lose their status if they leave the country for 3 years or longer, and in the event of an extended absence, must obtain a re-entry permit.
However, as a Japanese Citizen, you are not restricted on the amount of time you can spend outside of Japan. Additionally, travel can be more convenient as many countries do not require Visas of Japanese Citizens.
Requirements for Naturalization
1.Continued residence in Japan
The applicant must have lived in Japan for more than 5 years.
2.Must be over 20 years old
3.Be of good moral character
4.Financial stability
You or your spouse must be financially independent.
5.Agree to hold only Japanese citizenship
You would lose your own nationality once you gain Japanese citizenship.
6.Respect the Japanese Constitution
Not involved in political violence against Japanese government.
Required Documents
Application form (with 2 photos 5cm x 5cm)
Reason why you want to become a Japanese citizen (hand-written in Japanese by the applicant)
Resume
Written oath
Description of your relatives
Description of how you make your living in Japan
Maps of the vicinity of your residence and workplace
Description of your business (If you or your family member is a business owner)
Financial statements
Business license
Company registration
Diploma
Domestic family documents
Proof of citizenship (birth certificate)
Certificate of employment
Certificate of residence card
Certificate of tax payments (with hold slip, income tax returned record)
Certificate of your assets (bank deposit, real-estate, securities)
Driving record
Others upon requirement
Actual Procedures for Naturalization
First, consult the Citizenship Division at your local Legal Affairs Bureau
Collect all the required documents
File an application in person
Acceptance of application
The Legal Affairs Bureau checks the application
Interview at the Legal Affairs Bureau (a few months later)
Permission will be given by the Minister of Justice
Announcement through the Official Gazette
Effective as of the announcement day
Naturalization certificate will be issued
Return your alien registration card
Report to the municipal office to create the family registration
Change your name (bank account, driver’s license etc.)"