Well I really don't watch much Asian baseball, but I dug around and found this site
MyP2P.eu :: Live sports and Now Playing overview. Free Live Sports right now on your pc.
The broadcasts are live and in Japanese or the native language of the live feed.
Here is the Official NPB English website for schedules, standings and some stats info.
Nippon Professional Baseball Official Website
Keep in mind Japan is thirteen hours ahead of U.S. Eastern standard time. For example when it's 1 AM here it's 2PM over there. Good Luck
Enjoy the Yokohama Bay Stars @ Hiroshima Toyo Carp live:
??? on Justin.tv
Catch Tokyo Yakults' Norichika Aoki; pictured my previous post (perhaps the best hitter in the NPB)
Chunichi Dragons @ Tokyo Yakult Swallows
ys_ch on Justin.tv
These game are live and I don't think you can watch them at a later time. Enjoy