This study used the functional resonance analysis method (FRAM) to analyze a real-world example of an emergency-response process, one that occurred in Koriyama city, Japan, during Typhoon Hagibis (known in Japan as Typhoon No. 19, or Reiwa 1 East Japan Typhoon). The analysis revealed nine functions that constitute the municipality's emergency-response process (including Public Communication, Provision/Management of Evacuation Shelters, Evacuation, and Rescue Operations) as well as the interactive relationships between these functions. It also revealed how variabilities in the timeliness and accuracy of the functions resonated with (reinforced) each other, culminating in an incident involving a backlog of emergency calls. From these results, two recommendations were derived: reviewing the public communication system and building a framework for minimizing variability in evacuation behavior. And also, based on the FRAM analysis we could contextualize the interview data and the individual phenomena described fragmentally in the retrospective report (used for evaluating the disaster response), thereby gaining an understanding of the incident generation mechanism. In conclusion, the study demonstrated FRAM can be an effective tool for retrospective evaluation of disaster response or revising a disaster plan.