Shintai-zan Mountain (神体山)
Shintai-zan Mountain is a term mainly used in Shitoism meaning a mountain believed to be where deities dwell in the concept of mountain worship and also called Kannabi, a mountain where deities dwell.
Such sacred mountains are also called 'reiho' (lit. sacred peak), and Mt. Fuji is one of the representative reiho. Passes, slopes and other small peaks were also considered sacred and worshiped as places where deities dwell.
Summary
According to the idea of animism in cultural anthropology, the mankind viewed the phenomena of life and death in an objective manner, created a recognition of 'life' as a concept of ego and consciousness out of such a view, and considered life, deity or spirit dwells in living creatures as well as in natural objects such as mountains, rivers, rocks and trees. This understanding also applies to Japan, and deities of higher ranks are believed to dwell in big things or things that live long in Shintoism and particularly Ancient Shintoism that is also called Jomon Shintoism for it is believed to have existed before the beginning of the Jomon period (ancient form of Shintoism that existed before the 6th century before it was influenced by the foreign customs and forms folk beliefs in today's Japan).
What typically represents such idea is mountains, and the idea that deities dwell in particularly big unique mountains is known as mountain worship. Mountain worship is found not only in Japan but in various parts of the world; the Masai and Kiyuku tribes in the southern part of Kenya worship Mt. Kilimanjaro as a mountain where their god abides. Other examples include Mt. Everest, Jade Dragon Snow Mountain, and Uluru (Ayers Rock) are worshiped by Sherpas in Tibet, the Nakhi in Yunnan Province, China, and Australian Aborigines as their holy mountain, respectively.
In Japan, kannabi, a holy mountain where deities dwell, is another form of mountain worship. Formerly mountains worshipped as kannabi include ordinary mountains and iwakura (dwelling place of a god, usually in reference to a large rock) or iwasaka (the area a deity sits) as well as volcanoes and bold mountains with no forests. The name "kannabi" then came to be given to mountains covered with trees and forests and adjacent to human communities, and such mountains came to be called "Chinju no mori" (sacred shrine forest) or "himorogi" (primitive shrine, originally a piece of sacred land surrounded by evergreens), while "iwakura" became sacred rocks as rocks, unique rocks, big rocks such as "meoto-iwa" (husband-and-wife rock). Today kannabi is said to have become the antetype of tamagaki (fence around a shrine) for Jinja Shinto (Shrine Shinto) together with himorogi.
Today many 'shrines' in Jinja Shinto stand at those holy places worshipped in the idea of ancient Shintoism, and sainokami (guardian deities) were changed from nature or natural elements to humanized divinity called 'mikoto.'
This explains that many ancient shrines were originated from the Shintaizan (kannabi) worship. This idea is evidenced by the theory that the basic layout in Shinto building construction style, which is the order of 'torii - main building - Shintaizan,' and that this order is established even in cases where a Shintaizan is located behind worshippers by considering the approach to the shrine. This idea is explained by other theories. The theory proposed by Wataru IKEBA that shrines in Ancient Shintoism traditionally built as places of incantation or festival in large communities were modified by the influence of Buddhist concept and that the 'idea of permanent presence of deity' as presented by the enshrined deity always dwells in the main building of the shrine was born also agrees with the explanation that shrines were built at places of Ancient Shintoism. Haruki KAGEYAMA interprets that it began as ancestral worship like kofun (burial mound) or tsuka (ancient tomb) and was then transformed into natural Shintoistic form that sees a mountain itself as the object of worship and that in due course of time the concept of ancestral deities in mountains was fused with the concept of agricultural deity.
Subsequently mountain worship in Ancient Shintoism was fused with Esoteric Buddhism, Zen Buddhism, and Taoism (Onmyodo, or Way of Yin and Yang, which is an occult divination system based on the Taoist theory of the five elements), and tohai (mountaineering for worship) under Shugendo (Japanese mountain asceticism-shamanism incorporating Shinto and Buddhist concepts) became active.
Holy Mountain Fuji
Ancient anecdotes about the deities of Mt. Fuji and Mt. Tsukuba are recorded in "Hitachi no kuni fudoki" (the Topography of Hitachi Province). The parent deity visited the deity of Mt. Fuji and asked for lodging, but the mountain deity rejected the request on the grounds that the deity was during fasting. The parent deity then went to Mt. Tsukuba, asked the deity of Mt. Tsukuba for lodging and was welcome this time. Consequently, many people began to gather at Mt. Tsukuba; on the contrary, Mt. Fuji came to be always covered with snow, and people stopped visiting Mt. Fuji.
According to "Honcho seiki" (Chronicle of Imperial Reigns), Matsudai (Fuji Shonin) buried Issai-kyo (Complete Collection of Scriptures) on the top of Mt. Fuji in 1149, and the buried scriptures, believed to have been unearthed atop Mt. Fuji, are enshrined at Sengen-taisha Shrine.
"Sarashina Nikki" (Sarashina Diary), a literature work in the Heian period, wrote that some people in those days believed the personnel affairs for the following year in the Imperial court were determined by the deity of Mt. Fuji.
The area of Mt. Fuji higher than the 8th station is the compound of Sengen-taisha Shrine except for the climbing trails and Mt. Fuji Weather Station. But no land registration is yet done because the prefectural boundary between Shizuoka and Yamanashi is still undetermined.
Mt. Fuji Hongu Sengen-taisha Shrine
A top Mt. Fuji are located Okumiya (interior shrine) of Mt. Fuji Hongu Sengen-taisha Shrine dedicated to the deity of Mt. Fuji and Konohanano sakuya bime.
Konohanano sakuya bime is also known as the 'deity of fire.'
But according to the legend handed down by Mt. Fuji Hongu Sengen-taisha Shrine, this goddess is known as the 'deity of water' that suppresses fire. When and how the deity of Mt. Fuji came to be identified with Konohana sakuya bime is unknown.
Fujiko (devotional Fuji confraternities) and Fujizuka Mounds
In the Edo period, climbing Mt. Fuji for worship became widely popular among commoners. This practice is believed to have begun as the worship of Mt. Fuji exercised by Tobutsu KAKUGYO (1541 - 1646) who conducted ascetic practices in a cave at the foot of Mt. Fuji from the Sengoku period (period of warring states) to the beginning of the Edo period (from the latter half of the 16th century to the early half of the 17th century). As a result, commoners came to strongly worship Mt Fuji, and many Fujizuka mounds for worship of Mt. Fuji from afar were built at various parts of Edo. Fujizuka mounds are artificial mounds constructed by filling up earth and were built at places that can command Mt. Fuji, and Sengen-taisha Shrine was built atop those mounds. Those mounds were designed to allow people who couldn't visit Mt. Fuji to experience climbing Mt. Fuji and worship it on a simulated manner.
In response to the growing popularity of Mt. Fuji worship, various new religions mixing Shintoism and Buddhist based on the Mt. Fuji worship were born in the Edo period. Those new religions conducted missionary work in Edo and formed Fujiko confraternities, and some such groups became too big to be ignored by the Edo shogunate government, which eventually announced directives to prohibit formation of Fujiko confraternities repeatedly. For example, the Edo Magistrate's Office announced the directive to prohibit Fujiko seven times from 1774 to 1849. Some of those new religions still survived the hard days of the Meiji era and are still operating, which include such groups as Jikko-kyo, Maruyama-kyo and Fuso-kyo.