I went through Japan twice, and we were only ushered to the next gate. Nothing required but boarding pass and passport so this is why I question.
Oh yeah. Your question is totally acceptable. I think I learned more about transit visas here on VJ than anywhere else.
It has to do with the amount of hours in the layover. Japan and Turkey are some of the countries that sometimes request transit visas for people of specific countries (not to everyone). For example, in Turkey, if they are not staying overnight, you don't need a transit visa... otherwise, you do.