Mount Kōya (高野山, Kōya-san) is a large temple settlement to the south of Osaka. In the strictest sense, Mount Kōya is the mountain name of Kongōbu-ji Temple, the ecclesiastical headquarters of Shingon Buddhism.
Kūkai (空海; 27 July 774 – 22 April 835), also known posthumously as Kōbō Daishi (弘法大師, "The Grand Master who Propagated the Dharma"), was a JapaneseBuddhist monk, civil servant, engineer, scholar, poet, artist and calligrapher who founded the esoteric Shingon school of Buddhism.
He travelled to China, where he studied Tangmi (Chinese Vajrayana Buddhism) under the monk Huiguo. Upon returning to Japan, he founded Shingon—the Japanese branch of Vajrayana Buddhism. With the blessing of several Emperors, Kūkai was able to preach Shingon teachings and found Shingon temples. Like other influential monks, Kūkai oversaw public works and constructions. Mount Kōya was chosen by him as a holy site, and he spent his later years there until his death in 835 AD.
"According to the superstition of the Shingon Buddhist school, there are no dead in Okunoin, but only waiting spirits. As the story is told, one day Kukai (774-835), better known in Japan under the name of Kobo Daishi, the founder of the religious community of Mount Koya, came out of meditation upon the arrival of Miroku, the Buddha of the future.
So all the souls in transit resting in the graves or of whom the hair or ashes had been placed by their loved ones in front of the Kukai Mausoleum, also rose up. Pending the advent of this apocalyptic prophecy, the number of graves in Okunoin continues to increase and already counts more than two hundred thousand and is the largest cemetery in the archipelago." (source: Japan Experience)
Danjōgaran at the heartland of the Mount Kōya settlement and contains the main sacred buildings: a main hall, several pagodas, a scripture storage, a bell tower, a lecture hall, and other halls dedicated to important deities. There is also a shrine dedicated to the Shintō-gods of that mountain area and in front of it an assembly hall (Sannō-dō). Danjō Garan is one of the two sacred spots around the Mount Kōya