So, Japan buys some islands in the China Sea. China doesn't seem to think that they were for sale, however...
The islands in question straddle some shipping lanes, are near potential energy finds and, perhaps most importantly, when you say "Japan" to the Chinese, they don't picture today's smilingly polite and increasingly geriatric producers of Hondas and Hentai, but rather a swarm of hard-faced killers decapitating everything they didn't rape at bayonet point. The Japanese, in turn, feel about the Chinese pretty much the way they feel about everyone else who isn't Japanese.
Two legs of this love triangle are nominally our allies, and the third has nukes and a bunch of our IOUs. Were I Japan, I wouldn't be making any moves that required Uncle Sam to hold my coat right now, given the decisive command team in the White House, where apparently people have to be practically chased down hallways and arm-barred into making foreign policy or national defense-related decisions, which will then probably be changed or modified within 48 hours anyway.
This could get interesting.