There have been various attempts at establishing a business social networking service in Japan in the past years, but none of these have taken off.
In September 2007, LinkedIn inked a deal with Tokyo-based web company Digital Garage to bring the service to Japan, but that never happened (LinkedIn founder Reid Hoffman is still a member of the advisory board though).
The Japanese Wikipedia page on social networks has a short list of Japanese business social networks, but again, almost no one uses these:
One of the main reasons for the absence of business social networks in this country is that for Japanese web users, online privacy is very important. For example, most users don’t reveal their real names or pictures on Mixi, Japan’s Facebook – in the light of this, a service like LinkedIn, which requires members to reveal their entire work history, has a hard time gaining a foothold in Japan.