A major Hachiman shrine located on top of Mt. Otokoyama, a few miles south-west of Kyoto at the site of a pure rock spring (iwashi-mizu). According to onmyo thought it protected the city from the dangerous influences of the south-west (as the Buddhist Enryaku-ji protects from the north-east). It was established as the result of an oracle of the Usa Hachiman-gu revealed to the Buddhist priest Gyokyo. Hachiman is revered at Iwashimizu as an ancestor of the imperial clan, through his identification with emperor Ojin.
A Popular Dictionary of Shinto. Brian Bocking.