Depends on where you live. If you are from Austria, Australia, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, the Netherlands, New Zealand, Norway, Portugal, South Korea, Spain, Sweden, Switzerland, or Great Britain, you just have to take an eye and physical exam. However, if you are from China, Brazil, the United States, or a country not named above, you have to take a written exam and the driving test. No matter what though, you will not be able to simply use your country's drivers license in Japan. However, if you plan ahead of time, and are only going to be there for under a year, you could always get an IDP from your country.