<![CDATA[Multilingual practices among young children are increasingly common in multilingual families and play an important role in language acquisition development. This study aims to describe the stages of Ritsuki's language acquisition, the forms of multilingualism employed, and language dominance in daily communication as observed in content from the "Ueno Family JAPAN" YouTube channel. The research subject is Ritsuki, a child from an Indonesian-Japanese mixed family. A descriptive qualitative approach was adopted, with data derived from Ritsuki's speech in three purposively selected videos from the "Ueno Family JAPAN" channel, collected through observation, listening and note-taking, documentation, and video transcription, then analyzed through data reduction, data presentation, and conclusion drawing. The results, based on an analysis of 24 speech data, indicate that Ritsuki is in the "simple sentence stage," characterized by the use of simple sentences to convey questions (7 data), commands (1 data), refusals (1 data), and information (1 data). The forms of multilingualism identified include Indonesian (9 data; 37.5%), Japanese (5 data; 20.8%), English (1 data; 4.2%), and code-mixing between Indonesian and Japanese (9 data; 37.5%). Indonesian emerged as the most dominant language in Ritsuki's speech, particularly in communication with the mother (Umma), with Indonesian-language elements present in 75% of all data when combined with code-mixing instances. These findings confirm that a multilingual environment and the intensity of language exposure from family members play a significant role in the diversity of children's language use. From a psycholinguistic perspective, this study offers insights into the relationship between language acquisition, syntactic development, and multilingual practices in young children growing up in a multilingual family environment, while also carrying implications for parents and educators in supporting children's optimal language development.]]>
