This study examines how five multilingual teaching assistants use daily digital interactions to build communities, manage face, and construct identities in a KakaoTalk group chat. Analysis of 442 messages collected over 5.5 months (September 2025 – February 2026) revealed systematic changes: task-focused talk decreased from 32% to 7%, while social talk increased from 19% to 42%. Using qualitative discourse analysis with quantitative frequency tracking, this study identified five recurrent practices: emotional support (8.1%), apology and responsibility management (2.7%), task coordination (20.1%), leadership implementation (4.5%), and cultural sharing (1.6%). A single conflict in October was resolved through a distributed apology (9% of monthly messages) and increased support (13%), illustrating collaborative facework (Goffman, 1967). Drawing on communities of practice theory (Wenger, 1998), relational approaches to politeness (Locher & Watts, 2005), and computer-mediated discourse research (Herring & Androutsopoulos, 2015), the analysis shows that, although English is a shared language, participants draw on culturally embedded resources: Korean members use Korean-specific emoticons, the American member uses global common emojis, and the Uzbek member shares cultural references in 4.1% of their messages. This study contributes to multilingual academic communication research by demonstrating how digital communities form and negotiate their identities on KakaoTalk, an important non-Western platform.