Case is one of the most salient grammatical properties of natural languages, and it would not be too much to say that since the advent of the Case Theory by Vergnaud [Foundational issues in linguistic theory: Essays in honor of Jean-Roger Vergnaud, ed. Robert Freidin Carlos P. Otero and Maria Luisa Zubizarreta. Cambridge, MA: MIT Press (1977)] and Chomsky [Lectures on government and binding. Dordrecht: Foris (1981)], theories of syntax have been constructed and improved on the basis of the newly discovered properties of morphological case and abstract Case in European languages and Japanese. However, the spread of various types of electric corpora, the activation of field works and typological studies, and the subsequent growth of comparative and diachronic syntax have enabled us to realize how complex a system of case/Case is even in a single language, how radically it has changed in a single language, and how many micro-variations there are across languages, all of which have given a non-trivial impact on the theories of case/Case, syntax and linguistic theories in general (Crisma & Longobardi (2009)). This chapter summarizes the history of the major theories of morphological case, abstract Case, and related issues; introduces a brief summary of each of the subsequent chapters of this book, half of which is about the case/Case in Japanese; and demonstrates how each chapter can be placed in the theories of case/Case, syntax, and linguistics.