The threat from Mt.Fuji is not only its impending eruption. There are also mudslides and giant boulders that can come tumbling down at any moment. The name Ō’ishi means “large rock”, deriving from the rocks that often fall down around the teahouse due to large mudslides. It is said that the Kakugyō Rock in Sengen Shrine is a result from one of those rockslides.

The Ō’ishi Teahouse came about in the Taishō period when the people of Fuji-kō financed and supplied tools to build the teahouse. Proof can be found in the stone monument dedicated to the “Fuji-kō” faith.