Population decline is leading to a shrinking city size in industrialized countries. In some developing countries, because majority of the population is concentrated in big cities, the population in undeveloped cities has begun to decline. Japan experienced rapid urban expansion surrounding industrial districts, including steeply sloped areas, between the 1950s and 1970s. In the past forty years, Japan’s population has decreased, and the average age of the population is increasing. The reduction in the size of cities, following population decreases is becoming an important issue, and the study of sustainable, concentrated urban planning to cope with shrinking city size is, therefore, necessary. We have conducted a case study using Yahatahigashi-ku to determine its redevelopment potential, based on a combination of urban geographic data. This paper (1) presents a typical case study using Geographic Information System (GIS) data to evaluate an aging and shrinking society; (2) explores the GIS design approaches configured for an aging society; and (3) evaluates the optimization of environmental performance for an urban regeneration plan. The primary factors related to this urban design case study included, a declining population, mixed urban land use, and the placement of public facilities. We developed a method involving the slope degree to evaluate land-use to model the importance of informational evaluation in the urban planning process. This method could contribute to the urban regeneration for an aging society and could also be applied to other aging and shrinking cities, in mountainous regions.