I regularly send and recieve mail from the UK to friends in cities all over Japan: Nagasaki, Tochigi, Kawaguchi... both large packages and small envelopes, and the mail always arrives at the destination. Japan's postal service is seamless, and should not be in question. I know from experience that it is awesome, they are second to none and VERY fast. We're not talking about Russia or Ukraine here.
I had received contact from ibill recently about a check that was returned to them - in the signup field, I had forgotten to change the country field, and the check was mailed to my address but had USA specified as the country, which is all wrong.