This study explores the operational mechanisms of brand communication and relationship management within Vietnam's small and medium-sized restaurant sector. Focusing on "A Seafood Restaurant" in Lao Cai Province, Vietnam, as a single case study, the research collected qualitative data through semi-structured interviews based on the "5E stakeholder framework" (owner, managers, head chef, experts, and customers). The researchers conducted thematic analysis and a triangulation test. The findings reveal a dynamic, three-stage cyclical process: in the "information exposure and initial awareness" stage, customers primarily establish initial trust and purchase motivation through word-of-mouth recommendations and social media, although current social media management tends to rely on passive exposure; in the "consumption process and trust accumulation" stage, on-site "customer interaction" (such as guidance during ordering and attentive service) and "relationship management" (such as promptly addressing negative feedback and improving processes) are critical to solidifying brand loyalty; finally, in the "relationship deepening and cyclical diffusion" stage, a positive physical dining experience translates into positive electronic word-of-mouth (eWOM), driving secondary dissemination. The study's conclusions align with the "communication-based relationship model," confirming that managing small and medium-sized restaurant brands involves more than one-way promotion; rather, it relies on the interplay between interactions at physical touchpoints and relationship repair mechanisms. Based on these findings, the study offers practical recommendations for local restaurant operators regarding brand communication and customer retention.