And they have a bunch of useful local services and since ebay does not exist in Japanese the next big thing in Japan is Yahoo auctions which is pretty, pretty big.
Huh. Didn't realize that after the Verizon acquisition, it lost all ownership ties with Yahoo. So future readers don't have to click through:
Yahoo Japan was always a separate company, a joint venture between Yahoo and SoftBank. When Verizon acquired Yahoo, the bits that Verizon didn't want - including Yahoo's share of Yahoo Japan - were spun off into a holding company, Altaba. And so now SoftBank and Altaba between them own most of Yahoo Japan.
