What should declining Japanese cities do?

Aging societies and population decline have been on the rise globally, but in Japan, the situation has been exacerbated ten-fold. A staggering 36.21 million people, or 28.9% of the populace, are 65 and over. Further, 74.6% of Japan's 1,747 cities are categorized as shrinking, with urban policies struggling to keep up with the decline. However, the factors that correlate with population changes in cities of varying sizes have not been clarified.