Not my area of expertise, so I'll out-source. James Fallows comments and points to Karel van Wolferen's detailed analysis.
It could be a paradigm shift. Or not. But if the election does represent a new direction for Japan it should not be taken lightly. As Walt says:
After all, Japan is still the world's second largest economy. Its military spending ranks fifth in the world. It has a highly educated populations and many advanced industries and scientific establishments (including the potential to get nuclear weapons very quickly if it wished). It is the location of several key U.S. military bases, and is bound to Washington by a long-standing security treaty.
All this means that if Japanese economic and foreign policy were to change significantly, the effects would be quite far-reaching. I'm not saying they will, but I am planning to spend a bit more time keeping an eye on events there.