Previous studies have statistically examined the social and psychological factors that influence the adoption of individual-level flood adaptation measures, focusing on the role of social networks in implementing these measures. Effective communication policies were explored in the Netherlands and France by simulating the diffusion of adaptation measures through social networks using empirical decision models and agent-based simulations. However, similar research still needs to be made available in Asia. This study investigated effective communication policies in Japan by simulating the diffusion of individual-level adaptation measures through social networks. Unlike the Netherlands and France, the results revealed that people-centered communication policies were less effective in Japan, while top-down policies proved more successful. At the same time, social networks were critical in adopting adaptation measures across all regions studied. Empirical decision models and agent-based approaches can provide valuable insights for developing effective communication policies to promote flood risk adaptation on a global scale.