In July 2009, Yahoo signed a deal with Microsoft, under which Yahoo was to adopt Microsoft's Bing as the search engine on all Yahoo sites. However, Yahoo only has a minority stake (35%) in Yahoo Japan, while the Japanese telecom giant Softbank owns 40% of the company, meaning that Yahoo didn't have the final say in the decision.
"Yahoo! Japan made this decision as an independent and separate publicly traded company... This decision by Yahoo! Japan does not impact the global rollout and implementation of the Yahoo! search alliance with Microsoft, except in the Japanese market," Yahoo said in a statement.
Now, in a deal that is likely to be challenged by Microsoft, Yahoo Japan and Google will corner the Japanese search market, in which Bing only has a minute share.