Effective disaster risk reduction requires the implementation of innovative disaster technologies. In spite of substantial investments in money, time, and energy, innovative disaster technologies have yet to be implemented. The reasons for poor implementation remain unclear. The majority of existing disaster preparedness studies do not examine real-life, already implemented, or adopted disaster prevention technologies or practices. An individual’s intention to prepare differs significantly from their actual preparation. This study argues that, in order to obtain a comprehensive understanding of the diffusion of disaster preventive technologies, it is essential to examine the social networks of key players. In contrast to focusing on individual cognitive characteristics, social networks provide a more comprehensive understanding of the social construction of preparedness. This study examined how the organizational structure and network development process facilitate the implementation of rainwater harvesting technology in Sumida-ku, Tokyo.