The conception of the separation of Shinto and Buddhism is recognized as early as in Nihon shoki. The scandal of Usa Hachimangu Takusen by Dokyo (which occurred in the era of Shotoku Tenno, when the idea of the harmony of Shinto with Buddhism had reached its peak), caused a crisis of royal authority, which in turn prompted the separation of the two. As the result the separation was institutionalized in the Chotei Saishi, and especially in the Tenno Saishi, which are rituals included in the Jogan-shiki of the 9th century. After the middle of the Heian Period, this separation spread widely to regions other than just religious ceremonies, although the harmony of Shinto and Buddhism had also developed vigorously. The belief that the genealogy verifies that the Tenno blood descends from Amaterasu Omikami forms the religious ground for the "raison d'etre" of Tenno and the nobles, and this concept is embodied in the rites of the Tenno Saishi. Thus, if the matters and affairs connected with Buddhism were allowed to be part of the Saishi, it means that the view of monarch sovereignty in terms of Buddhism is accepted officially. This is exactly where the crucial factor of the separation of Shinto and Buddhism lies. It is considered that the institutionalization of the separation in the 9th century was influenced strongly by the awareness that Buddhism had deeply infiltrated into the Court, and by the idea that Japan is the "land of the gods, " which had been enhanced by the sense of crisis related to foreign threats. The separation of Shinto and Buddhism was not confined only to Tenno Saishi, however. It had penetrated deeply into the society of the nobles, and furthermore, it had taken its root as a norm in the society of the common class people. This became the basis on which the Shinto of today is formalized.
