The rocks are located at the top of a 333-meter-high mountain about 9 km southwest of the city. They were discovered in 1903, and in 1917 a branch of the Soma Myoken Shrine was enshrined there.
The couple rocks are lined with three rocks of different sizes, a 10-meter high "male rock," a 10-meter high "female rock," and a smaller "child rock," all shaped like stacked planks.
The rock type is hornblende andesite, and it is estimated that the lava erupted on land around 13 million years ago, long before the appearance of humans, as a result of volcanic activity. The lava may have been eroded over time to form the present three separate rocks, or the three rocks may have been piled up separately to form the present three rocks.