The present study examines interjections in Sino Japanese classrooms and the pragmatic functions, the cultural factors, and their function in promoting inter cultural communication. Classroom observations, semi–structured interviews with teachers and students, and transcripts were thematically coded. The pragmatic functions of interjections, particularly agreement, hesitation, politeness, and topic management, and the cultural norms of Confucian hierarchy and wa (harmony) were investigated. Participant interaction and real time discourse analysis were also used to examine code switching and hybrid interjections. Findings indicate culturally determined interjection patterns in the Sino-Japanese classrooms in which Japanese students tend to frequently and concisely use phrases like “はい” and “うん” to maintain harmony and Chinese students favor formal and subservient expressions of “嗯” and “对” as a means of recognizing authority. In the hybrid contexts, emotional responses (agreement, hesitation, politeness) and code switching ("嗯…oh wait, そうだね") were accompanied the pragmatic functions of interjections (agreement, hesitation, politeness, and topic management). Cultural assimilation emerged through peer alignment, identity negotiation, cultural blending (Japanese, Chinese, Western) to navigate hierarchical teaching structure and create a shared learning space. Expressively, interjections serve as dynamic communication tools—to etch the individuals involved as well as to script the cultural norms and identity negotiation within the Sino–Japanese classroom.