The purpose of this paper is to understand the multiple social structures of a kaison, or seaside village, by presenting a case study of Okaura, one of the kaison-villages that consists of two (an urakata and a kamakata) and is located on the coast of Ise-Shima. To clarify the characteristics of Okaura, the historical background of each community, the relationship between the inhabitants, the natural environment, and the balance between “insistence" and “concession" towards the rights in their ordinary life will be analyzed. First, the case study of the urakata, a fishing community, shows that it is characterized in terms of social structure as equalizing and categorizing rights through an original ritual system (Touya-system) and a unique fishery system (Amikabu-system). It is further characterized by domination the Ise Grand Shrine and solidarity with the neighboring fishing villages. Second, the case study of the kamakata demonstrates the community's multiple social structures through its founding legend and a network with Youkagama (eight villages engaged in the salt industry). The relationship between the urakata and the kamakata is also influenced by both the village's natural resources, such as salt, wood, and marine products, and also by the environment itself. Moreover, their relationship has changed through time with flexibility. Okaura, as a kaison-village, has a multiple social structure consisting of both an urakata and a kamakata structure. The case of Okaura suggests that the village structures are very complicated and dynamic in the small seaside area.