Years ago, I commissioned a Japanese translator from Hawaii to convert sample questions and a summary of the Driver Handbook into Japanese. This material has been sufficient for Japanese-speaking people to pass the written test.
For the record, I was working for another driving school when this work was commissioned. My boss was horrified that I traded driving lessons for this service, but he accepted it as my decision. When I started my own business, I referred many Japanese customers to my former employer because he had the material and I did not. Two years ago, a co-worker gave me a stack of papers in Japanese. They were the same papers from years before! So I kept them. They came back to me so I could help people get a Guam License. Click here for the PDF file.
It has sample questions, road sign information, safe driving tips and a summary of the Driver's Handbook.