There has been a sharp increase in the number of foreigner registrations in Japan with a record of 2.5 million at the end of 2017, which is an increase of 7.5% on the previous year. Japan is going through a rapid transition politically, socio-culturally and economically, and this has inevitably had an impact on everyday language life and landscapes in Japan. Drawing on everyday interactional data from Tokyo, a site which has increasingly become socio-culturally and linguistically diverse due to the incoming flow of people, goods, ideas, practices and language, this chapter shows that in order to understand everyday linguistic diversity in the city (in this case Tokyo), or what we call “metrolingualism”, we have to explore both the idea of space and of diversity in greater depth. This chapter argues how metrolingualism’s enquiries into everyday language use from a local perspective and its focus on the dynamic relations between semiotic resources, activities, artifacts and space (i.e., special repertoires, metrolingua francas and metrolingual assemblages) as people go about their daily lives, provide a new way of understanding multilingualism in the city and the sense of affordance brought about by multilingual practices. This approach is particularly important where people are left in an ambivalent space between the Japanese government’s animosity towards the proliferation of cultural diversity and the everyday reality of cultural and linguistic diversity, and argues that metrolingualism can offer Japanese sociolinguistics a new perspective during this critical time of transition.