Yahoo Japan's search results is now identical to Google's in many cases if you use Chrome browser. In other words, depending on which browser you use, you get different search results in Yahoo Japan right now.
Yahoo Japan and Google Japan jointly announced that Yahoo Japan's organic search results will soon be powered by Google. However, it looks more of the hybrid version rather than the pure Google search.
Search results can be quite different when you search in different country, even when you use exactly the same search term. Here are examples of the search results in US vs Japan.
Yahoo Japan had algorithm update in December 2009, which caused many to experience ranking changes. This article is about the apparent changes from the latest update.
How to localize the forms for Japanese market so that you won't lose people came to your site and ready to register or order for stupid usability mistakes.