This book pays special attention to municipal variations within the same prefecture, presenting a completely unique approach from what other researchers have pursued. Taking the Goki-Shichido (Five Home Provinces and Seven Circuits of Ancient Japan) as a theoretical framework, this book examines shrinking Japan from a regional variation perspective by municipality along the ancient Sannindo, which comprises eight provinces, and four prefectures today. The study identifies the principal explanatory factors based on the small area data of e-Stat through GPS statistical software tools such as G-census and EvaCva, within a historical perspective. This historical knowledge helps in understanding the significance of the regional cultural heritage that remains in each municipality today.  This book studies two present-day prefectures along the ancient Sannindo for detailed analyses of the impacts of regional variations of population decline in Japan. They are northern and central parts of Kyoto Prefecture, made up of the former Tango and Tamba provinces, and Tottori Prefecture, formed by the ancient provinces of Inaba and Houki. The reasons for selecting these two prefectures of the ancient Sannindo are twofold. First, they are made up of a multiple number of the ancient provinces. Second, other prefecture that fall under the Sannindo, i.e., Shimane Prefecture has been studied in the previous works of the present author by adopting the same methods of analyses. Thus, by presenting unique analyses of regional variations on small municipal levels in Kyoto and Tottori prefectures along the Sannindo, this book offers suggestions for effective regional policy to revitalize shrinking Japan to a sustainable one.