Japan has nuclear weapons?
I sure hope so. . .
http://www.globalpost.com/dispatch/news/kyodo-news-international/140126/us-asks-japan-return-plutonium-exported-during-cold-wa
http://www.nytimes.com/2014/04/10/world/asia/japan-pushes-plan-to-stockpile-plutonium-despite-proliferation-risks.html?_r=0
If not, Japan has the technology to produce advanced thermonuclear weapons in short order and China knows it.