I googled japan fallout and came across this which was posted in 2009.
Originally posted by another user
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Over in San Francisco at the Game Developers Conference, a little sit down was held with a few respectable game developers.
Of the group, Emil Pagliarulo revealed that Bethesda Softworks is currently working on some more Fallout 3 downloadable content as well as the next Fallout.
Emil asked himself: “What famous landmarks can we destroy? What landmarks in Japan can we destroy?” Then after the crowd laughed, he said “I just realized how stupid it was of me to say that.” Could Fallout 4 bring a post-apocalyptic Japan to our homes?
Kinda messed up after what's happening right now but I thought it was a good find lol.