Last month, Japan’s defense ministry requested a record budget of about $51 billion for fiscal 2017. At the top of its security worries: China’s maritime aggression.
Japan has reason to worry. In both the East China Sea and South China Sea, Tokyo faces an increasingly assertive China that looks determined to become an unfettered maritime powerhouse—and is beefing up its naval capabilities accordingly.
China’s moves threaten to disrupt Japan’s economy and erode its sense of security. The South China Sea is not the only sea route, but it offers the cheapest, most direct way for energy supplies from the Persian Gulf (and other commodities from elsewhere) to reach northeast Asia. As a nation with few natural resources, Japan has a clear interest in keeping sea routes open.

http://qz.com/780317/japan-and-china-are-ramping-up-maritime-tensions-in-the-south-china-sea-and-east-china-sea/