An interesting read but I think he misses one big thing: death taxes.
These are about 50% in Japan right? Half of all that saved money invested in bonds and postal savings will be taken by the gov't as the baby-boomer generation dies off. Half the value of all the real estate and other investments too. It's not a cure but as most of Japan's debt is internal (gov't bonds) I think the next 50 years will see a considerable reduction in bond-debt just from death taxes.