This study examines the life story of Ms. S, a second-generation Japanese who remained in Sakhalin and returned for permanent residence in Japan, to clarify the significance of her linguistic experiences from the viewpoint of mediation in plurilingualism and pluriculturalism. The study thus discusses the significance of mediation in plurilingualism and pluriculturalism within multicultural societies. We interviewed Ms. S, one of the second-generation Japanese who returned to Japan for permanent residence in City A, about her life story, and conducted an analysis from the perspective of to what extent she learned and used the language. The results revealed that Ms. S’s mediation activities have the following roles: “the role of connecting the people of Sakhalin with Japanese society,” “the role of connecting Japanese and Russian speakers,” and “the role of conveying the experiences and memories of the remaining Japanese in Sakhalin to Japanese society.” Further, it was also clarified that mediation was connected to the renewal of Ms. S’s identity, which is possible precisely because she is on the boundary between languages and cultures. Based on the above results, we discussed the necessity of creating a place for the mediation activities of plurilingual and pluricultural speakers in a multicultural society.

Backgrounds of increasing numbers of immigrants represent “superdiversity” (Vertovec 2007) and in sociolinguistics, attention has been paid to immigrants’ individual linguistic repertoire. By interviewing such people, we aim to examine how they self-evaluate their proficiency and use of their host society’s dominant language through their contact experiences with the host society, how they construct their identities, and to reveal part of how their linguistic repertoire is formulated. The narratives of 10 participants were analysed regarding their proficiency self-evaluations and identity. We found that overall, there were more similarities than differences in the trends of their self-evaluation of their host language proficiency and use in both countries. The results on their identity indicate a close relationship between the participants’ identities and their contact experiences in their host society. Moreover, we claim that the participants’ narratives on identities allow us to predict the direction of their linguistic repertoire construction. This type of in-depth examination of individuals’ repertoire will give us an important suggestion when we consider concrete language policies towards immigrants.