In this post, I will delve into the how public debt can lead to a crisis, particularly in the context of Japan The basic issue here is that the Japanese government has depended on an ultra expansionist monetary policy and large fiscal subsidies in order to try and alleviate its economic stagnation with little effect, and the above continues to threaten the credibility of the yen, particularly as the dead cycle continues to accelerate. While much of the debt is domestic, there is still a foreign component to the debt and to investment in Japan, and the depreciation of the yen erodes The consumption and investment power of Japanese firms and households, with wages being virtually stagnant in Japan for so long. The Yen is already being attacked by speculators, though small ones, and if wage increases eventually go through, which pressure for will build if purchasing power erodes, fiscal costs for subsidies will rise.

With such a large public debt then and the likely continued monetary tightening globally, Japan does not have many good options long-term. It either has to go through a sustain period of high inflation in order to reduce debt coupled with austerity measures by cutting government expenditures, or else go into a potential sovereign debt crisis if interest rates have to rise. Sure, Japan can keep taking on debt if interest rates are near zero or negative, but interest rates have to rise eventually, And part of the reason why interest rates have not risen yet to the detriment of the Japanese economy is because the central bank is thinking about this large public debt and the impact that interest rate increases would have on it.
In this case, the size of the public debt does matter, notwithstanding the boarder impact such debt has on the economy.
Really, it's just somewhat strange that the notion that public debt does not have economic consequences remains, especially with the number of debt crises across the world right now.
Most of which being public debt.