What I'm trying to say is that there are ways of achieving this without that privacy issue, since you're trusting Japan Post with your address anyway. See my other comment that I replied to this thread. It seems like the design itself is fundamentally flawed when a different approach could allow people to maintain their privacy while also achieving convenience. I say this as someone who actually lives in Japan, and after thinking about it for a few minutes, has come to the conclusion that this is probably not going to fly - Japanese people don't like the idea of a national ID at all, and are very sensitive to privacy concerns.