If the appetite for JGBs in Japan starts going down, the government will have to start looking abroad to cut their deficit. Things could get very interesting.
I also wonder how Japanese pensioners view the "inflation target". If you are setting on a pile of cash, zero inflation or a mild deflation is not a bad thing. Your pension is not going to increase, so having each yen go a bit further than last month is not necessarily bad. Inflation will encourage consumption in the short term of course, but it may also result in economic hardship when pensioners find that their yen does not stretch as far as it used to.
I think the Abe government is walking a fiscal tightrope. If their policies result in hyper-inflation, we will have trouble. If they do nothing at all, the poor demographics and stagnant economy will lead to trouble.
I wonder if they could have used their election mandate to focuse on improving productivity, making it easier for women to hold full time jobs and for immigrants to live and work in Japan. I guess printing money is much easier politically!
(Disclaimer - I too live in Japan).
Edit - Corrected JTBs to JGBs thank you J_