How to sign up to Yahoo Japan Auctions - information working as of 5th Aug 2007.

- Please note, this signup will allow you to view auction items, including items which have closed. Also, by completing the verification at the end, you can see auctions in the adult category which can't be seen without an account.
I do not know how well the account will work for actually bidding on items and such, I've been advised that there may be a nominal fee involved if you wish to bid over a certain amount on Yahoo Auctions, but I don't have any confirmation or knowledge of the matter, and I don't know the language enough to seek a confirmation.
Personally I use the account for simply getting around the restrictions placed on viewing closed or adult auctions, I bid through a deputy service (Shopping Mall Japan if you're interested).

First head to the Yahoo Japan Auctions website at http://auctions.yahoo.co.jp/jp.

Near the top, there's a notice saying (In Japanese of course), "Hello Guest (Login here)" Click the link.

Most of the left half of this next page is ads and the like, on the right is the login box, and underneath that, the Register link. Click that.

The next page lays out the multi-step challenge to progress through the ranks and become the ultimate champion of Yahoo!.
Really it just tells you you need to sign up for a Yahoo! ID, and then set up the account for auctions (which in our case will be taken care of automatically), beyond which is confirmation of the email address we provide. After these three steps is optional stuff like Premium membership which I wont go into.
Click the first step.

Now we're into the meat of it, the signup page.
Hopefully you can follow the instructions I provide in the pic below.
The balloon over the username wont show unless you click the Check Availability button, but the Foreign Resident balloon will show as soon as you put 000-0000 in the postcode field. 000-0000 is shown in the tips on the right of the page as the postcode to enter for foriegners, so there's nothing wrong with using it, it's just an advisory popup.
Choose the bottom option for all drop down boxes EXCEPT the Date of Birth one, use the top one there. That one sets it up for years counting from 0AD instead of aligning it with Emperor reigns like the other options.
If you want to access Adult items, make sure your age is over 18.

Once submitted, this next page just tells you what has been set up. You've got a username, a new email address (which you never need to use), and an online profile (again you don't need to use).

Note that at this time an email will se sent to the registration email address. Don't click links in it, the one which looks like a confirmation link is actually a "Hey I don't remember signing up for this, get me off your list" link. Confirmation links come later

Clicking the big green button takes you back to the Yahoo Auctions page, and you're already logged in.

Now you can browse Yahoo Auctions just like before, and you can also bid for stuff too! But it's no use as almost every auction wont ship international or accept paypal.

If you're happy with just that, THE END. But of course you made the account for a reason right? That's right, you want to access the Adult category, not available without an account.

What we need to do now is attempt to access the Adult category, as this triggers the next step.
From the category list on the left click "Other" () and on the next page, click "Adult" ().

Hooray, back to the roadmap. You'll see the first two steps are marked off (when did we do the second? It is a mystery), and now we need the third, confirmation of our registration email address. Click the link.

This next simple little thing is just asking "Do we really want to send an email?" Well of course we do, click the button.
Once you click, the screen will change to show that the email is being sent.

To your email client! Note that you now have two emails from Yahoo! The first is the "Someone used this address to sign up a Yahoo! ID", and the second is "Yahoo Auctions wants to confirm this address" (not actual translations, but you get the gist).
Open the Yahoo Auctions one and click the link that starts "http://verify.yahoo.co.jp/v/full?"

Excellent, this last page of this guide just says that the email address is confirmed, and that shiny green button leads back to the adult category, now open for your virgin eyes to explore.

Have fun!