Having first appeared during the Nara period (710–794), jingū-ji remained common for over a millennium until, with few exceptions, they were destroyed in compliance with the Kami and Buddhas Separation Act of 1868.
Seiganto-ji is a Tendai temple part of the Kumano Sanzan Shinto shrine complex, and as such can be considered one of the few shrine-temples still extant.
One of the first efforts to reconcile pre-existing Japanese religion with Chinese Buddhism (in what would later be called shinbutsu shūgō, or amalgamation of kami and buddhas) was made in the 8th century during the Nara period with the founding of so-called jungūji or shrine-temples, religious complexes consisting of a shrine and a temple.
We know that the temple part of the shrine-temple complex consisted of several buildings, among them a main hall (honji-dō (本地堂)),[note 3] a pagoda, a Buddhist gate (mon) and a betsu-in (別院, the monks' residence).
[9] At the end of the 8th century, in what is considered the second stage of the amalgamation, the kami Hachiman was declared to be tutelary deity of the Dharma and a little bit later a bodhisattva.
[3] Shrines for him started to be built at temples (giving birth to the so-called temple-shrines), marking an important step ahead in the process of amalgamation of kami and Buddhism.
[3] When the great Buddha at Tōdai-ji in Nara was built, within the temple grounds was also erected a shrine for Hachiman, according to the legend because of a wish expressed by the kami himself.
[6] Hachiman considered the shrine his due reward for having helped the temple find the gold and copper mines from which the metal for the great statue had come.
[6] After this, temples in the entire country adopted tutelary kami (chinju (鎮守/鎮主), enshrining them in specially built shrines called chinjusha (lit.
The improperly-named institution traditionally called "Twenty-two Shrine System" was in fact a network of shrine-temples under Buddhist control.
Because mixing the two religions was now forbidden, both shrines and temples of shrine-temple complexes had to give away the parts of their properties which were now illegal, thus damaging the integrity of their cultural heritage and decreasing their own historical and economic value.
[11] Its giant Nio, the two wooden wardens usually found at the sides of a temple's entrance, being objects of Buddhist worship and therefore illegal where they were, were sold to Jufuku-ji, where they still are.