As anticipated, today Japanese Prime Minister Abe successfully approved a Constitutional change that allows Japan the use of force to protect itself and its allies.
The rule of pacifist Japan had been imposed by the US after the Second World War. As China is rising, it fits perfectly for the US to let (or push) Japan to re arm for its new strategy of unleashing regional rivalries (like Saudi/Iran) instead of being the world policeman. It is definitely cheaper, if riskier.
Again, this is another tectonic shift in this new millennium. It is not that we will pass immediately from a pacifist Japan to a fully militarized Japan, but Japan will be a force to be reckoned with in the Pacific (still in peace time it had the 6th largest military budget in the world).
Definitely China will notice and things around the Seniauku island will be hotting up. And now also Japan can start serious military collaborations with the Philippines, Vietnam, China