kurogane wrote: ...
Yokohammer,
I agree, but what I was asking was whether it is actually a legal requirement to do so, not a reasonable and practical compromise, though I fully agree with you, always do so, and never mind when asked, though I have had a few Okinawan cops be rather brusque and presumptuous, which hurt my feelings.
My understanding is that it is a legal requirement. Cops, immigration officials, coast guard ... you are required by law to produce on request. Hotel desk staff can go fuck themselves (unless you're temporary and have no fixed address in japan).
Back in the good old days when our Alien Registration cards were actually little booklets, that requirement and the attendant laws were printed in it. That was before smartphones, of course, so if you really needed something to read on the train, there it was.