Abstract Objectives While studies have examined the effects of large-scale disasters on disaster-vulnerable individuals, these analyses may not capture the full impact. This study qualitatively explored the impacts of the March 2011 Fukushima triple disaster on patients with breast cancer and their families, aiming to highlight the importance of incorporating family narratives to grasp the full effect of large-scale disasters. Methods Utilizing the medical records from two hospitals, deceased patients with breast cancer from the disaster period were identified. Relatives were interviewed using a semi-structured approach. Thematic analysis was conducted via the Braun and Clarke method and Taguette transcription software. Results Interviews with seven family members of six patients revealed three main themes: the family’s caregiving burden and their deepened bonds with the patient, the patients’ extensive medical challenges and their physical and mental decline, and the shared confusion during the disaster due to resource shortages and evacuation dilemmas. Conclusions This study uncovered significant infrastructural issues such as reduced medical support and the heavy caregiving load on families, amidst some strengthened relationships during a time of crisis. Future research should investigate these issues across various disaster contexts, and proactive measures should be implemented to prevent exacerbation of these challenges.