This study aimed at verifying a hypothesis regarding the polarization to megacity regions and the urban divide. In the first part, we examined the polarization to megacity regions in Japan focusing on concentration of wealth based on various economic statistics, as well as records of public investment. In the second part, we selected Osaka city as a case analysis for examining the urban divide inside a megacity region (based on a cluster analysis) and analyzed the current conditions of the urban divide in Osaka City. In the third part, we examined the diverse types of living in the Airin area, Nishinari Ward, Osaka City. Through analysis based on interview surveys conducted at local real estate companies, we discussed the mechanisms in housing provisions for realizing of diversity. Urban divides (in both social and spatial terms) are clearly observed in Osaka City. In particular, the Airin area of the Nishinari Ward in Osaka City is the area where daily construction workers are concentrated, and many of workers in this area are old and/or have lost jobs. Simultaneously, the Airin area functions as a place to nurture diversity, as a gateway to the city.