This document provides an introduction to a textbook on teaching Japanese as a foreign language using a communicative approach. The textbook aims to explore issues related to language learning theory and research, provide an overview of communicative language teaching, and suggest communicative tasks and activities for teaching Japanese grammar. It also aims to encourage empirical research on teaching and learning Japanese as a second language. The textbook is divided into three parts. Part A provides background on second language acquisition research and its implications for Japanese language teaching. Part B discusses communicative language teaching and approaches for designing grammar and communicative tasks. Part C introduces classroom-based research methods like experiments that can be applied to studying Japanese acquisition.