Why is Tokyo Osaka and Nagoya densely populated?

Tokyo, Osaka, and Nagoya are densely populated due to their status as major economic and cultural hubs in Japan. They offer abundant job opportunities, advanced infrastructure, and a high standard of living, attracting people from rural areas and other regions. Additionally, effective public transportation systems facilitate commuting, making these cities more accessible. Their historical development and concentration of services and amenities further contribute to their high population density.