Japan may take matters into its own hands

“China has been helpful,” Trump said, but it is clear that the president expects China to do more. During the interview, he revealed that he told China that Japan may take matters into its own hands if Beijing doesn’t find a way to stop Pyongyang, an apparent reference to Japanese rearmament and militarization.

“Japan is a warrior nation,” the president explained to Ingraham. “I tell China, ‘Listen, you’re going to have yourself a big problem with Japan pretty soon if you allow this to continue with North Korea.”
http://dailycaller.com/2017/11/03/trump-to-beijing-warrior-japan-may-act-on-north-korea-if-china-fails/

take matters into your own hands
​to deal with a problem yourself because the people who should have dealt with it have failed to do so:
https://dictionary.cambridge.org/us/dictionary/english/take-matters-into-your-own-hands

さあ大変だ！（爆ｗｗｗｗｗｗｗｗｗｗｗ