With the increase in linguistic and cultural diversity in South Korea, the landscape of English education in Korean classrooms has been changing. This has led to an increased need to explore the language and literacy practices of the emergent multilingual youth in Korea where one (official) language (Korean) has been predominantly used as the medium of instruction for English teaching and learning. Addressing this need for more research on how emerging multilingual children learn English in the diverse Korean classrooms of today, this four-year longitudinal case study explored out-of-classroom English language learning experiences of three Uzbek students in South Korea. Drawing upon the conceptual framework of "translanguaging" and "agency," data were collected from various sources. I found that the actions taken by these students to learn English depended on their interlocutors, practical and academic purposes, and language ideologies embedded in contexts, which in turn influenced learners' agency and translanguaging practices. More specifically, the findings show the students exercised agency over their choice of linguistic and non-linguistic resources in order to expand their linguistic repertoires on their own accord. These findings provide implications for EFL research and pedagogy, particularly within the context of the transition from monolingual to multilingual.