Memorial facilities are one of the crucial places where citizens conduct activities facilitating disaster risk reduction (DRR). However, previous studies have primarily focused on the post-construction phase of official memorial facilities, neglecting the citizen activities collaborating with the official memorial construction process before and during the construction process. This research gap is important considering the urgency of disaster-affected regions to recover from spatial, social, and psychological voids while working towards the goal of DRR, including the efforts of citizens in the official efforts. This study addresses this gap by examining the case of the official memorial park in Ishinomaki, Tohoku region, following the Great East Japan Earthquake. Here, local citizens actively participated in activities before, during, and after park construction, engaging with official efforts. Data were gathered from various online sources to capture activity, space, and management information. Employing a mixed methods research approach, we conducted both quantitative analysis, counting labels of structural coding, and qualitative description of original texts. Our findings reveal that fostering mutual respect built on communication and collaborative tree-planting activities were crucial for maintaining the pre-existing citizen activities and collaborative construction during the official construction period. Additionally, the implementation of a collaborative regulation system was vital for integrating and managing spontaneous citizen activities to achieve the park’s intended objectives post-opening. In conclusion, we highlighted a framework elucidating the mechanisms through which these processes contribute to DRR across key phases of disaster risk management: preparedness, prevention, response, and recovery (PPRR). These insights are important in guiding efforts to engage citizens in DRR initiatives through recovery and reconstruction facilitated by memorial facilities.