The cavern where Takkoku no Iwaya Temple is built is said to be the place where Emishi people, who used to have a reputation for violent behavior, once set up a fort.
In 801, Sakanoue no Tamuramaro, under order of Emperor Kammu, travelled to this area as a conquering general and defeated the Emishi after a fierce battle. Sakanoue no Tamuramaro, who felt that the victory was thanks to Bishamonten, built a nine-room, four-sided temple that imitated the stage of Kiyomizu in the cavern as a token of his gratitude for Bishamonten. It enshrines 108 statues of Bishamonten and is a place of prayer to calm the country. The circumstances relating to the Emishi and Sakanoue no Tamuramaro have become part of many stories and traditions, and also add colour to the temple story of Seikoji Temple.
The precinct of the temple is considered a sacred space and eating, drinking, collecting flora and fauna, killing animals, and visiting with dogs and cats is strictly prohibited. It is a strict space that sets it apart from the surrounding idyllic landscape.
To the left of the Takkoku no Iwaya Temple is a large Buddha carved into the rockface. It is a large statue called the Ganmen Daibutsu with a height of about 16.5 metres and a shoulder width of about 9.9 metres. It was allegedly carved by Minamoto no Yoshiie to memorialise the spirits of the enemies and friends who died in the Zenkunen War and Gosannen War.