You will need a passport valid for your entire period of stay in Japan.
This certifies that you are able to financially support yourself while staying in Japan. If you will be working, your employer will help you obtain this document. If you are not working, you need financial records or a bank statement proving you can fund your stay in Japan.
You will need to prove that you will have some form of health insurance while staying in Japan. International insurance plans are readily available on the Internet, and Japan's Global Health is a popular option for foreigners.
Applications can be downloaded at the Japanese Embassy's website.
Certain applications may require additional documentation. If you are applying for a spouse visa, for example, you must submit your marriage certificate. Check with the Japanese embassy to make sure you have all the required documents.
