From the drastic changes of twentieth-century modernization, Japan is experiencing a visible and public recognition of the diversity of languages and new awareness about language, ethnicity and ways of belonging in Japanese society. Bilingualism is emerging as a key instrument of social change. It is being reformulated both as a way of being in multicultural society and as a platform for vigorous discussion about educational needs and practice. In 2017, the number of Japanese first language speakers was reported to be 128 million. This number includes, crucially, speakers of mixed linguistic and ethnic background as well as non-Japanese nationality. Keywords in the evolution of bilingualism in Japan include language standardization and assimilation to the Japanese language, the presence of the nikkeijin (immigrants of Japanese ancestry) and (Chinese-speaking) war orphan bilinguals, “internationalization” and bilingual education. Given its historic vision of social homogeneity and monolingualism, an ideology not restricted to Japan, the nation is experiencing new challenges in formulating effective frameworks for bilingual education and language education in general. These challenges encompass multiple stages and sectors of the social system and are dependent upon factors of time and resources. Bilingual education in Japan raises questions of both individual learning as well as language maintenance and language loss, language endangerment, language death and revitalization. A recurrent theme in the current sociolinguistic milieu is the nuance and layering of speakers’ personal needs (“languages are signs of belonging”) where identities are locally constructed and negotiated.