We have less research data on the structural aspect of temples and devotees of established Buddhist sects than that of the doctrinal aspects, which have their own history. The purpose of this paper is to understand the structure and movement of the Otani sect of the Shin denomination, one of the leading sects of established Buddhist orders in Japan. It is natural that the established order should have dual organic characters, that of the devotee as well as that of the order. The Otani sect had firmly formed its own character by the Edo period, and after the Meiji period, reformed the confraternal meetings (ko) of the devotee, first established by Rennyo, a great leader of the sect. Ko meetings were the foundation of the structure and movement of the sect. The Otani sect was controlled and protected by the government under the imperial (tenno) system. After Japan was defeated in World War II (1945), the Otani sect, which has its foundation in the rural areas, was forced to meet changes in the sect itself, and tried to form a new movement of the devotee named the Dobokai (society of brethren). But it stagnanted under the influence of the feudalistic character inherent in the sect. Even with such problems, the Otani sect has continued to maintain its traditional rituals and temples. However, it is certain that the Japanese population will diminish in the near future, and we cannot predict how this will affect the structure of traditional Buddhist organizations.