I thought the US problem was more based on the fact that those mortgage haz the always-up value of the house as collateral. Creating a self feeding downward spiral when people were defaulting-trying to sell-lowering property value...
Since in Japan houses are disposable and only the land keep a somewhat steady value I don't see how the problem can be as big.
But then again, I choozed to be communist because I dramatically failed economy 101 from kindergarden to university, and I still quite suck at anything involving money... (but my last cat was free from the parking, so in a country were they cost between 10man and 25man I was kinda sorta feeling like the king of wallstreet... (and is a very good cat also...))