Answer:
some ideas: racial biases, cultures, political/economic factors
Japan is facing a labour shortage
Step-by-step explanation:
Racial Biases - People in a certain country may have certain racial biases against people of another country (examples could be believing people of one race are lazy, troublesome etc)
Cultures - Certain cultures in some countries want a "pure" population where they are unwilling to accept immigrants from other countries in order to protect their population
Political/Economic factors - Western countries are becoming more polarized in their political opinions and opinions are now starting to be taken to more extreme lengths. A certain political party may promote notions that allowing more immigration would increase competition in the job market (taking away jobs from citizens) or that accepting more immigrants would lead to a greater tax burden on citizens who would have to pay for social programs/services. Most factors can be encompassed into this political/economic reason.
Japan is a facing a labour shortage and a population decline. They would need immigrant populations to come and fill the missing labour roles in the country.