An international driver’s permit is valid for up to one year or until it expires. All residents who plan to drive in Japan must obtain a Japanese license within 1 year after entering Japan. Requirements for applying for a Japanese driver’s license vary depending on the country in which you were previously licensed to drive.
Licenses from certain countries require both a written and a driving test in order to get a Japanese license while certain countries may be eligible to obtain a Japanese license without taking the written and driving test.
If your home country’s international driver’s permit is not accepted in Japan, you would need to immediately apply for license conversion.