It is called Mitsuishi(3 rocks) shrine because gods reside in the 3 gigantic rocks in the mountains.
In Japanese mythology the 3 gods are enshrined, and the 3rd rock was made to be the rock of marriage.
If you can tie a ribbon through the many small holes in the rock, it is called tying your relationship. In recent years the ribbon is tied through a 5 yen coin.
In Japanese “good relations” and the Japanese 5 yen coin both share the same pronunciation “Goen” and that is how it started.
Established in 1185- 1190.
Photogrammetry from 989 photos taken with D750 and RX100Ⅱ in Nov. 2019
Address is Tadami Town, Fukushima Prefecture,Japan
Form more information: https://www.tadami-net.com/mitsuishi.html (5 languages)