Driving in Japan
Americans cannot drive in Japan with only a U.S. drivers license. Persons found driving in Japan without a legal license are subject to fines, arrest and possible deportation.
"International Driving Permits" are not a medium-to-long term substitute for a Japanese driver's license. You cannot obtain an Internation Driving Permit at the Embassy; see below.
You cannot renew your U.S. license at the Embassy. Renewal by mail is available from some states; find out more for your state here.
International Driving Permits (IDP)
"Residents" are expected to convert or obtain a Japanese drivers license. Persons using an international drivers license who are resident in Japan can be subject to fines or arrest. The exact boundary between "resident" and "not resident" is unclear. In practice it seems to involve more than simply visa status or length of stay in Japan and is determined by the police.
We have heard from several Americans who were told by the police that using an International Driver's License for more than a year, or using one after exiting and then returning to Japan, or using one when you are residing in Japan, or after you have obtained an Alien Registration Card, or after 90 days in Japan, or using a license obtained by mail while you are in Japan, is illegal. In two instances, following accidents, Americans were charged with driving without a license, a serious offense. Driving without a license may also void your insurance coverage.
Obtaining an International Driving Permit
An international driving permit issued in the United States by the American Automobile Association (AAA) or the American Automobile Touring Alliance (AATA) is required of short-term visitors who drive in Japan.
International driving permits (IDP) are not issued by the U.S. Embassy or by its consulates.
IDP's must be obtained prior to arriving in Japan. They cannot be obtained in Japan.
Note that IDP's are not intended to replace valid U.S. state licenses and should only be used as a supplement to a valid license. In other words, you must also have a valid U.S. state license in addition to an IDP to drive in Japan.