A history of the Japanese language is a well-structured, comprehensive, and beautifully written monograph on the development of the Japanese language. It is divided into four parts that focus on four linguistic periods (Old Japanese, Early Middle Japanese, Late Middle Japanese, and Modern Japanese), which coincide with political periods in Japan's history. These four parts are divided into seventeen chapters. While each part is structured coherently with the main focus on phonology and grammar, specific topics characteristic of different periods, such as writing, reading, and loan words, are discussed.

Part 1 describes the oldest attested stages of the Japanese language of the Nara Period. Beginning in Ch. 1 with early forms of writing, such as phonographic writing (e.g. man'yōgana), this part goes on, in Ch. 2, to consider the early stages of sound inventory as well as morphophonemic processes (e.g. vowel deletion and rendaku). Ch. 3 explains the grammar of Old Japanese, detailing the parts of speech, conjugation classes, and particles. Ch. 4 outlines Ainu and continental (e.g. Korean) loan words. Part 1 ends with a brief look at dialects from eastern parts of Nara in Ch. 5.

Part 2 explores the Early Middle Japanese of the Heian Period (794–1185). Ch. 6 focuses on the writing systems, especially the emergence of kana. Ch. 7 offers detailed explanations of syllable structure, segmental sound changes, and prosody. Ch. 8 presents grammatical aspects that went out of use or changed function, as well as forms that newly emerged. The main sections are the morphology of the inflected forms and the functions of kakari-musubi ‘hanging-tying.’ Ch. 9 focuses on the practice of reading and writing Chinese texts, showing how the Chinese language was transformed into Japanese through grammar. Hentai-kanbun ‘deviant Chinese text’ is one example of this practice.

Part 3 offers a thorough description of Late Middle Japanese that reflects the Kamakura (1185–1333) and Muromachi (1333–1573) Periods. Ch. 10 provides a short summary of works written in these periods, including grammars and dictionaries. Ch. 11 presents, thanks to Christian sources, an established picture of the phonological system. In this period, the phoneme /p/ changed to /f/ and long vowels began to emerge. Ch. 12 deals with grammatical changes in both morphology and syntax. Kakari-musubi began to decline during these periods, and as a result, the exclamatory form that co-occurred with it ceased to be used. Honorific language, both exaltation and politeness, is discussed briefly in this chapter.

Part 4 moves on to examine Modern Japanese from the Edo Period (1603–1868) to the present. Ch. 13 provides a short summary of the language of the Edo and Meiji Periods (1868–1912). The former was characterized by the diversity of often mutually unintelligible dialects, while the latter strived to unify this diversity. Ch. 14 describes phonological changes, such as the merger of /d/ and /z/, as well as the delabialization of /f/ that gave rise to /h/. Ch. 15 illustrates two aspects of the development of Modern Japanese: (i) how it underwent grammatical simplification, and (ii) how new grammatical forms emerged. Ch. 16 highlights some influences of eastern dialects on Edo Japanese. Ch. 17 provides a bird's-eye view of loan words from European languages. Overall, this part is devoted to the period before World War II.

This monograph provides a rich and detailed description of the changes that the Japanese language has undergone since its earliest forms in the Nara Period. It is a monumental work that will be of value to scholars and students who are particularly interested in the phonology and grammar of the Japanese language.