This case study research examines the impact of transmedia storytelling on the global reach of Korean-pop (K-pop) group BTS (Bangtan sonyeondan) and how narratives within the transmedia storyworld can motivate the audience to seek individual and social change. This study is inspired by the rise of BTS in the global music industry. The group came with a solid brand image, highlighting sincerity and authenticity that captivate audiences worldwide. BTS consistent messages—that intersect with sustainability issues—about the importance of loving oneself, equality, social justice, anxiety, and wellbeing are communicated through multiple platforms and travel across language and cultural barriers. To understand the context, this study uses the concepts of transmedia storytelling and audience engagement by Jenkins (2006, 2007, 2012, 2014), Gambarato (2019), Broesma (2019), and Askwith (2007), to name a few. The method used to conduct this research is the analytical and operational model of transmedia design by Gambarato et al. (2020). The findings are that transmedia storytelling —with spreadability, drillability, extractability, and immersion characteristics—is an effective communication strategy that significantly influences the global reach of the group. Further, the camaraderie between BTS and ARMY generates fan activism—an epitome of individual change due to the fondness to BTS, as the act of identification and the attitude of giving back to the intimacy that BTS members provide to the fandom.