You should investigate some of the events that go on.

Here are some more internationally minded ones:

Tokyo2point0 - web related: http://www.tokyo2point0.net/

Business In Japan - general: http://businessinjapan.jp/

TLUG - Linux related: http://tlug.jp/

MobileMonday - mobile related: http://www.mobilemonday.jp/

Ninjava - General Technical - http://tech.groups.yahoo.com/group/ninjava/ (presentation tomorrow!)

For Japanese technical events, check out this calendar: https://www.google.com/calendar/embed?src=fvijvohm91uifvd9hr...

You could also check out Tokyo Hacker Space: http://www.tokyohackerspace.org/

Once you start participating in the community, you'll find more and more ways to meet other like-minded people.