I'm not familiar with the structure of the Japanese debt, but it seems that there's no major problem with it, since there's no attention coming from the mainstream financial media. I assume that Japan has lots of domestic debt and domestic debt isn't such a big problem, compared to foreign debts. I also assume that the debt has a pretty long term repayment structure. Most of the payments are postponed for several decades.
The biggest problem of Japan is not the national debt. The biggest problem is the bad demographics: less young people and more old people. This will cause a drastic change in the Japanese economy and social security system in the upcoming decades.
You pay that 10, and have 190 left, and use the rest of the money you have to build something. That is why Japan might be doing fine, because even though they have big debt, due to inflation and many other aspects, the amount they have to pay asap is not that big deal for them. Many nations have that, USA has that as well, it is quite ordinary to have debt.