There are a great many political, international economic reasons and I am sure most answers will centre around this. However the real reason is that the Japanese culture is dying from a failure to replace an ageing population. They have a declining population and cannot maintain their output, their living standard, their food production nor their infrastructure. And there is no solution for this.
Japan is facing a rice shortage in the coming years, as farmers age and die off. Young people do not want to be famers, or peasants. They want to live in the city with everything laid on.
Life in rural Japan may be scenic and pleasant, but the work is hard, backbreaking toil without the aid of modern tools and equipment. The farming methods are traditional, meaning backwards and inefficient. Indeed there are larger farms that use machines, but most farming areas are too tiny for this type of farming.
Many farmers are farming small areas of rice, maybe just 100 square metres, sowing and harvesting by hand, drying the crop on lines and winnowing by small machines.

Drying rice sheaves on a line
Because of the declining population 1 in 7 homes in Japan have nobody living in them. The outer neighbourhoods especially have lots of empty homes, used by the extended family to dump rubbish. Some westerners are buying up these homes for very little money, but they can only live there 3 months of the year.
So what can be done? The Japanese government is offering incentives for people to have more babies. They would do well to allow more immigration, but the Japanese people would rather see their culture die, than to become “diluted” with outsiders. Many say they are racist, but as a frequent visitor, I think it is more fear of losing the comfort and security of Japanese life.
Where everybody knows their place and how to behave. They simply don’t have there guts to become multicultural. Japanese life that reminds me very much like Australia in the 50s, governed by tradition, old wives tales, shame, religion and mother England.
I really think it would be very hard to be Japanese right now. It was bloody hard being an Australian prior to 1974. Many Australians opposed opening our borders, fearing that the influx of foreigners would kill the Australian culture, but it hasn’t happened yet.
Recently Japan has been in talks with China and South Korea for a mutual trading partnership. Considering these three countries hate each other’s guts since forever, this is indeed quite surprising, and commendable. But the reason is that both China and South Korea are having the same problem as Japan, only much more so. Especially South Korea.
Their births per woman are:-
China :- 1.18
Japan:- 1.26
South Korea:- .78
And you need 2.1 births per woman to just maintain a population.
People are still bleating about overpopulation, but in fact a bigger problem right now is population decline.
None of the developed world has a stable population. And as population declines, so will the standard of living, manufacturing, farming and civilisation.
In the 1950’s Australia started an immigration policy with the slogan “Populate or Perish”.
Well guess what?