What are the reasons Japan's population is falling?
I could literally list 50 reasons that contribute to the population drop, but it mostly has to do with high education, a lack of meaningful inflows through immigration, and certain social phenomena unique to Japan. All countries experience falling birthrates when they industrialize and embrace education -- the Philippines went from 7.5 babies to 3 born per female over the past 40 years for example. So it's largely a normal thing, just most pronounced here.