I've had an impossible time trying to update my 
credit card information (new expiration date). 
For some reason, doing what I repeatedly tried in 
the past seems to have suddenly decided to work! 
But now I have a "Yahoo Wallet" where I didn't 
before, and I'm waiting to find out in what new 
way I just screwed up my account. (If everyone 
knew how many times I've screwed up my own 
account while troubleshooting Yahoo Japan, you'd 
all be amazed I still have it. ^_^;;)

It should also be noted that, since I don't have 
a Japanese address, I don't have *any* address on 
file with Yahoo Japan. It's blank except for the 
zip code. (I don't know if knowing that might 
help you or not.)

But here is the link to changing the address 
information:

Go to the URL that I've posted above, and at the 
bottom you will see a link that reads "Changing 
your registered information".

If you click that link, you'll be shown a series 
of screen captures of Yahoo Japan that will show 
you the links to use to change your address. In 
the second screen capture on the page, you want 
the link that is the one for changing your 
password/e-mail address/etc. (They've put more 
links on this page since I made my screen 
capture, but the link you want is still the one 
on the top left.)

The place to click for changing the address 
information is shown in the thrid screen capture, 
the second block of information I bracketed. 
You'll see only my zip code (02703) there with 
everything else marked as being not entered.

Many Sharp Smiles,
--Drac