This book is one of the pioneering historical pragmatic studies of Japanese. It closely illustrates the usage and contributions of some Japanese discourse markers, and reveals their developmental history. The section on Synchronic Analysis explores the previously uninvestigated functions of some discourse markers used in Present Day Japanese. Moment by moment in on-going conversations, where culturally rigidly-defined interactional norms are highly valued, a specific marker is chosen and used by the speakers as their strategy, based on their quite subjective judgment. The section on Diachronic Analysis then demonstrates chronologically how the meanings and forms of the same markers have come into being. Results include some noticeable changes related to the strengthened intersubjectivity. This multi-dimensional study also discusses the relevance of findings to typological characteristics and productivity. Consideration is further given to why certain expressions (rather than others) become discourse markers and independent forms in Japanese.