For a visit of 90 days or less, only a valid passport and return ticket are required.
a USA citizen can stay in Japan for up to 90 days without a visa
No, a visa is not necessary, as Japan is in the visa waiver program, but that would require an ESTA from you.
Currently, Belgium is under the list of countries that are eligible for Visa Waiver program in the US. So a Belgian citizen need not apply for a visa to enter the US.
yes but it has to be an American visa.
No
no
You do not need a visa to travel to Japan if you are a US citizen. The purpose of your visit must be for visiting friends or family, touring the country or attending a conference. You can stay for up to 90 days.
Yes .
yes you do.
yes
yes
Yes.