Buy from Yahoo Japan Auctions

The differences between eBay and Yahoo are numerous.  The most important difference can be characterized by saying that Yahoo is a Seller's site and eBay is a Buyer's site.  Most of that has to do with protection and accountability.  Both sites are worlds apart when it comes with dealing with Buyers and Sellers and is, in my opinion, the biggest reason why the sites will not be able to have any kind of significant partnership in the future.  In the end it all comes down to a Japanese person's willingness to do international transactions, and that won't be changing anytime soon.

Practically speaking, you cannot.  There are so many hurdles to buying from Yahoo if you don't live in Japan that the hours and hours of time it would take you to find and complete just one transaction makes it impractical.  Perhaps you've heard of someone who was able to make an account, find a buyer to ship overseas, and work out all of the payment detail.  But what you probably found was someone who was interested in the personal challenge in seeing if it could be done.   There's nothing wrong with that if you want a hobby, but most people just want something they can only get on Yahoo or they want to save a few bucks getting it.