I went to a 2 person motorcycle license that I could ride together with my wife in order to avoid traffic congestion.
You can ride up to a 50cc motorcycle with a regular Japanese drivers license.
But it cant fit 2 people, and is only allowed to go up to 30 kmph.
You have to wear a helmet, of course.
So I spent 10 days studying in a classroom in order to get the next category up 125 cc motorcycle license.
It cost me about $700 USD, but I got my license today.
But it seems that I have to wait a year after getting my license before I can ride with another person...