Also, the largest search provider in Japan is Yahoo! Japan (2nd largest is Google, which has been slowly gaining).
Coincidentally, Yahoo! Inc does not own Yahoo! Japan. They are only a minor shareholder. Softbank is the largest shareholder of Yahoo! Japan.
Yahoo! Japan is also extremely different from Yahoo! that we know. In Japan, it's a social network, auction house, storefront, message board, news service and search provider all rolled into one. And they started doing this years before anyone else (becoming a one stop shop). The site may look dated today, but it was years ahead of its time when it started doing all those things. It's one of the reasons why they've been so hard to unseat. They got in early, sprawled out and cemented their place in Japanese web culture.