I was thinking about this the other day and i realized that they would be fine if they just exported key areas of their economy and kept the management portions in japan. Outsourcing would fix the labor issues. Keep only enough jobs for your own populace within national borders and just export the rest. The money from the foreign labor flows back home. Why not have other nations make up for the absense of your own young people?
Also, i think the senior crisis could be fixed by paying your elderly to go retire abroad. It would fix the healthcare aspect of elder care, and even the pension issues because the dwindling pensions would still support your populace wonderfully in those ASEAN nations.