While travelers from many countries can visit Tokyo and Japan with relative ease for 90 days on a tourist visa, make sure you follow the official Japanese government visa and immigration guidelines to ensure that you can enter the country legally. If you are from a country that requires a visa for entry into Japan—even for a short stay—be sure to follow the required procedures.
https://www.mofa.go.jp/about/emb_cons/mofaserv.html
Please look at the  list of the countries that have the visa exemption 
        agreement with Japan. If your country is included in the 
        list, you usually do not need to apply for an entry visa 
        to Japan.
        If your country is not included in the list, you need to 
        obtain a short-term stay visa (“tanki-shouyou visa” in 
        Japanese) from the embassy of Japan in your country.
        Read carefully the Japanese visa guide provided by the 
        ministry of foreign affairs. For entry into Japan, a 
        VISA may be required for ICMM 2020 attendees from some 
        countries. Please make sure whether you need to apply 
        for a VISA or not on the web site of Ministry of Foreign 
        Affairs of Japan at :
         http://www.mofa.go.jp/j_info/visit/visa/index.html