Japan equipped with [the F-35] will be better able to hold the door open in the face of Chinese attacks so that our reinforcements can flow into the western Pacific region if we are called on to fulfill our treaty obligations to allies in the region.
This article discusses the situation for Japan and explains that Japan doesn't really need to coordinate too much with America to enable our AirSea Battle-grounded Pacific strategy for pushing forces into the western Pacific:
The policy of Japan's Defense Ministry is in line with the view espoused by Gates. The policy focus of Japan is in the following three areas: ballistic missile defense, anti-submarine warfare and a hardening of bases against possible attacks.
The Defense Ministry does not believe it is effective or necessary to design an artificial bridge over the conceptual gap between the strategic plans of two countries, because as Japan makes progress on these three focus areas, Tokyo automatically can meet the expectations of the United States.
Exactly. If Japan can defend their air and sea space from China's air and naval power, and keep their ports and air bases operational in the face of Chinese missiles, Japan will enable our forces to arrive to fight at their side.