It's a bit annoying that the default it like that, but you can change it. On the Google search results page, click on the gear button, go to `Search settings`, and set `Region Settings` to Japan.
I ran into this when I was stuck using a connection that was detected as non-USA and was shared by people who would also be non-USA. I gave up using google search because I just could not get google anything to respect my requested region in a useful way. Even google maps on the web was problematic because it would constantly try to move the view right back to where it thought I was. It's quite annoying to search something like "$food near Massachusetts, USA" and get a list of stuff in Mexico one week and Canada the next.