They also have substantial foreign assets that can be sold. The situation in Japan is very unusual because the financial system has a massive synthetic net shor

They also have substantial foreign assets that can be sold. The situation in Japan is very unusual because the financial system has a massive synthetic net short JPY position. Because rates are so low, savings have been effectively dollarized in an economy that isn't dollarized (this is why USD/JPY is so correlated with rate differentials)...so I don't think anyone really knows how this will works out (there aren't a lot of historical examples, no country that held so many claims denominated in a foreign currency has been such a large part of the world economy...this is the end game of the export-oriented, mercantilist political economy...Germany is a ways down the same road). It makes no difference whatsoever that JGBs are held domestically in practice because it is harder to push through a debt restructuring politically when voters are the ones losing money (you have seen this in Italy too, they have "bailed in" domestic savers which has significantly reduced their options...if the debt is owned by foreign investors, you can usually restructure and point at them: look at these greedy capitalists, terrible...but we have no choice). On some of the other stuff mentioned above, the reason why Japan is in such a mess is because their financial/corporate sectors is totally screwed. There is no real demand for money, corporate balance sheets are loaded down with cash, no-one wants to invest, demand for money is so low that Japan's savings banks are huge players in US corporate lending, banks seem to have no actual capacity to make corporate loans...they don't know how, they just buy US bonds and call it a day, monetary policy (counter-intuitively) is making this worse, it is reducing the supply of "safe assets" but hasn't increased the capacity of institutions for "non-safe assets", it has led to a significant reduction in lending within Japan because rates overseas are so much higher...it is a real shit storm, but it all comes down to monetary policy officials not understanding money transmission (unusually for Japan, in the 1980s the govt was involved in directing lending on a loan-by-loan basis so they have a history of real control over monetary transmission).