Economics is not about math, precise and inevitable. Economics is about people and their social interactions.
Economists try to model social interactions with numbers, but don't mistake the map for the territory.
What does it mean in human terms that Japan has high debt? Is your argument that Japan will inevitably default? Sophisticated traders are willing to lend more money for 30 years at less than half a percent interest [1], so smart people must judge default risk to be very low.
Is your argument that somehow Japan is doomed because of this debt? Even if they default, what does that really mean on a human level? Would millions starve? Would society collapse?
Maybe Japan's history, customs, language and social cohesion are worth more than you think.
And, just for the record, Western stereotypes of Japan as a collectivist society are no longer true [2].
[1] http://www.bloomberg.com/markets/rates-bonds/government-bond...
[2] http://noahpinionblog.blogspot.com/2015/03/japan-is-not-coll...