No Japanese driver's license translation = no driving or renting cars and motorcycles in Japan.
Do you have a driver's license from Germany, Switzerland, Belgium, France, or Monaco? Then you absolutely need an official Japanese driver's license translation. The translation confirms to the Japanese authorities (police and driver's license offices) which specific vehicle categories and classes (e.g., small motorcycle, motorcycle, car) you are allowed to drive in your home country.
Attention: An international driver's permit (IDP) is not sufficient for these countries and will not be recognized. This is doubly annoying for holders of French and Belgian driver's licenses, as these two countries even signed the Geneva Convention, which is sufficient for all other countries for the IDP to be recognized.
You need the Japanese driver's license translation not only to drive vehicles but also to sign a rental agreement. Without a translation, you will not be able to rent a car or motorcycle.
More details can be found here: Why your international driver's license is useless in Japan