Table 1 Credentials and related information of the authors

Credentials of the first author

 Gender: Male

 Position: Associate Professor in the Department and one of the teachers responsible for the six-week intensive course in social medicine, including FTDA.

 Experience and academic career: The first author had a 15-year career as a researcher in the humanities and social sciences, specialising in qualitative research. He had experience in both participant observation and interview studies, and had published nine original research articles and one book. He had also been a lecturer on the social medicine fieldwork course for six years.

Relationships between the authors and participants

 Prior to the FTDA: Of the five participants, three individuals had a previous relationship with the first author, as the first author was a lecturer in the social medicine fieldwork class prior to the FTDA in 2015. The first author got to know them during this class. The other two individuals met the authors for the first time during the six-week intensive course in social medicine.

 During the FTDA: After completing the course assignments, as part of the pre-learning for the FTDA, the participants extensively studied papers and media reports on the FDNPP accident and occupational health issues for decontamination and reconstruction workers. All authors, including the first author, took part in this pre-learning as lecturers, which allowed students and authors to become familiar with each other.

 After the FTDA: Even after the completion of the six-week intensive course in social medicine, which included the FTDA, participants voluntarily visited and stayed in the department when they had questions related to social medicine, occupational health or medical statistics. Through these interactions, a continuous relationship was established from the time of the intensive course to the retrospective group interviews for the present study.