That's not a problem because most people want to live as long as they can. The problem's a drop in birth rates due to prosperity. Countries like the U. have been able to avoid that with immigration, but even next-gen immigrants also experience low birth rates.The biggest problem with Japan is they have the longest life span in the world at about 80 years. They have a huge older non working population that is dependent on the younger ones working. Most western countries are that way. Some older people can work longer, but some can't due to health and age related problems. Thus Japan is highly in debt. The US is getting that way, but welfare, food stamps, and welfare programs such as rent subsities, are a huge burden on society. Too many able bodied people not working. Right now in my area, fast food places all have help wanted signs. They are also paying more than minimum wage. When I was growing up these jobs were filled with teenagers working after school and on weekends. Today they are not. Omaha, Nebraska cut their crime rate by over 60% by working with businesses, schools, churches, and others to get teenagers jobs. This included violent crime. If this was practiced in most places teens wouldn't be getting into trouble, but earning money to buy cars or things they want, or like me paying my way through college. It is not encouraged today. If this happened young enough, many would get out of poverty and we wouldn't need so many immigrants.
Here is the crime reduction model news:
How one city cut gun violence in half and may become a model around the country - ABC News (go.com)
Japan is heavily in debt like the U.S. and many other industrialized countries because of late capitalism.
Crime is minimized given lower poverty, but the latter goes up given more poverty, and poverty goes up when population aging, lower birth rates, higher debt, and the effects of late capitalism take their toll.