This chapter explores the evolving health landscape in Southeast Asia, where communicable diseases have historically posed significant challenges. Primary Health Care (PHC) approaches have addressed local issues. However, with globalization, the Asia region has also seen an increase in people's mobility and digital transformation. The 2004 tsunami devastated entire communities, highlighting various social determinants of health. The reconstruction and recovery process necessitated the adoption of new lifestyles and coping mechanisms. This paper aims to discuss how people have managed their health and well-being amidst these evolving risks and what future collaborations are necessary to enhance community resilience and health outcomes in Japan and Asian countries from the 20th anniversary of the 2004 Indian Ocean tsunami. This study positioned mutual aid disaster risk reduction in a multicultural society as “primary health care focusing on social determinants of health in peacetime” and considered it as an interaction of multiculture from a nursing perspective. The study examined the principles of primary health care: person-centered strategies, equitable access, citizen participation, multisectoral collaboration, and appropriate technology utilization. The results underscored the need for comprehensive policies that strengthen networks with all people, especially vulnerable populations, regardless of the type or timing of the disaster.