Be serious Changing your citizenship is, obviously, a big decision. Japan doesn’t recognize dual citizenship, meaning by law you’ll have to renounce the nationality of your homeland. You will have to give up your old passport, and you may no longer be able to live freely, work, or in some cases, own property in your former country.
Get a job As wonderful as it is to freelance, Japanese bureaucracy puts a heavy emphasis on traditional full-time employment, and you’ll need to show on your application how you make a living.
Establish residency You must have been a resident of Japan for at least five years, as reckoned from the date of landing on your gaijin card. And don’t forget to get a re-entry permit if you leave; otherwise the counter will be reset.
Get married The easiest way to expedite the process is to marry a Japanese national. You will have a much harder time becoming a Japanese citizen if you don’t.
Learn the language You should anyway, but because you will be dealing with your immigration officer in Japanese and writing an essay about why you want to naturalize, you’ll need to have your speaking and (at least some) reading and writing in order.
Pay your taxes You’ll need to prove that you have made your contribution to society.
Behave Don’t get into any legal entanglements.
Get your papers in order Among other documents, you’ll need copies of your tax and financial records, birth certificate, parents’ birth certificates, parents’ marriage license and your marriage license.
Prepare yourself for the long haul Applying for citizenship is a trying process, designed to weed out applicants through attrition. You will need to meet multiple times with the immigration officer, so be ready to accommodate any extra requests.