This study examines the experiences of one Cambodian child’s Japanese language learning and heritage language maintenance, and explores his emerging multicultural and multilingual identities. Studies in Western contexts claim that linguistic and social identities have a great influence on bilingual language use, and consequently influence second language development and first language maintenance. Other studies argue that in multilingual settings, individuals negotiate their identities through discursive practices when positioned in particular ways by others. Through longitudinal observation of the Cambodian boy, this study shows that the child’s identities are multiple, a site of struggle, and subject to change. This project contributes to the field of second language education and global education by bringing together these various strands so as to improve policies and pedagogies to provide educational equality for multicultural children in Japan.