This book showcases a first-ever comprehensive understanding of sociological systems theory. What is specific to this volume is that, unlike many other books dealing with social systems theory, it focuses on the sociological aspect without being bound by a particular sociologist’s theory, especially that of Niklas Luhmann. The book does not concentrate on Niklas Luhmann’s theory itself, but on his ambition as a sociologist, that is, to build a universal theory of sociology with special reference to general systems theory, especially so-called second-order cybernetics. The main insight revealed here is that, facing the impact of globalization and the ICT revolution, we need an update of the existing sociological theories, including Luhmann’s. The author targets the definition of social systems as “observers” or “observing systems” in Luhmann’s literature. This is the most crucial point of sociological systems theory. After the theoretical updating,this book demonstrates how systems theory can be an analytical tool of sociology. The core analytical tool of sociological systems theory is the notion of “second-order observation” to society as an observer.  The book mainly deals with topics related to Japan, but at the same time it also shows the broad applicability of sociological systems theory.