The purpose of this study was to examine whether there are cultural differences in intimacy in friendships between Japan and China; and if so, to try to explain the cultural differences in terms of relational mobility. The results of a comparative study of Japanese and Chinese university students showed no cultural differences in relational mobility and intimacy between Japan and China. However, in the exploratory study, we examined the effects of two newly obtained subfactors of relational mobility on intimacy toward friends: "freedom to dissolve relationships" and "freedom to meet new people and form new relationships." The results showed that in Japan, freedom to meet new people and form new relationships was associated with a stronger sense of intimacy with friends, whereas in China, freedom to dissolve relationships was associated with a stronger sense of intimacy with friends. These results suggest that the two aspects of newly formed relational mobility may influence the intensity of intimacy with friends in each country through different processes.