In recent years, the number of people running to improve their health and physical fitness has been increasing. However, it is not easy to stay motivated and keep running as regular activity. Therefore, we believe that it is very significant to develop a running support system. In a previous study, a running assistance system that enables users to run with a virtual runner based on their own running records in an acoustic augmented reality space was constructed. In order to make the running experience more realistic and keep users motivated it is important to develop a system that allows users to compete with virtual runners who can serve as good rivals. In this study we examined how multiple virtual runners competing against the user affect the user’s motivation.