I am not sure I remember how long it would take for the Japan Post folks to kick any mail back to you, if that fella hasn't initiated the forwarding request with Japan Post, but maybe not such a long time would pass.
In the meantime we can see if any Yokohama (or close by) folks want to get in touch with you to offer brick-and-mortar style help, if that is allowed to be offered by the admin staff here and their policy on such.
And the Net world, besides here, might turn up something.
Actually, there's not much to thank me for, as I am just pounding some little buttons on this funny typewriter that seems connected to that big funny looking TV screen over there, but maybe somebody else can offer better help. Now I have to figure out how this thing my daughter called a 'Mouse' works to post this new message. (This thing sure don't look like no mouse.)