Kunio Yanagida and Shinobu Origuchi provoked a great deal of controversy regarding the Tokara Islands. But only few attempts have so far been made to address the problem of the social organization and cosmology, because early research of the area often fails to grasp the details. Since the problem of its cosmology was brought to light by Josef Kreiner, over the last few decades, its value system has become the subject of controversy. In recent years there have been a renewal of interest in social change. Although the ceremony of ancestor worship and mask ceremony have been an object of study for a long time, there is little agreement as to cosmology. This paper is intended as an investigation of social structure in Akuseki Island/Tokara, in which we are confronted by two difficulties. The first question to be discussed is why two different rites are practiced concurrently. The question which we must consider next is why they never correct the date of rites. These go to the very heart of the problems. The core of these questions lies in their folk ideology. In brief, the two rites function in a way that is mutually dependent. We may, therefore, reasonably conclude that a rite in this area is able to change, not only because of external influences, but also due to the traditional value system itself.