To enter Japan you must have a valid passport for the duration of your stay. Many countries have a "Reciprocal Visa Exemption Arrangement" with Japan. Please check the site below for information to see if you also need to apply for a visa before leaving for Japan.
inow2015 Registration Desk
c/o Kinki Nippon Tourist Co., Ltd.
Sumitomo-shoji Kanda-Izumi-cho Bldg.12F
1-13 Kanda-Izumi-cho, Chiyoda-ku, Tokyo 101-0024