Here is the common ground and controversy between most economists on the situation, I think it is interesting how much common ground there is: The common ground: * The government of Japan faces budget constraints; it cannot tax more than a certain amount and that includes seigniorage (taxing using inflation). * Right now Japan doesn't seem to be immediately close to those constraints since interest rates and inflatio…
There's so much about your post which is incorrect that I don't have time to debunk it all. So let me just hit the biggest error, so that others don't have to waste their time: It's literally impossible for Japan to default on their debts, which are almost completely in Japanese currency.
This definitely doesn't mean that it is impossible; at a minimum, a country might choose to do it. In fact as others have pointed out, default is sometimes preferable to hyperinflation and extreme devaluation. After all, all countries, Japan included, rely on imports to get at least some essential goods (think about food, fuel, medicine and tools); autarky is possible, but very inefficient and painful.