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 Sannyodo, which comprises eight provinces and four prefectures today. The book 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.