In this article, I explore some of the ways that the Heart Sutra is used by mountain ascetics in Dewa Sanzan, a sacred mountain range in Yamagata Prefecture, Japan, where I conducted twenty-four months of intermittent ethnographic fieldwork between 2012–2019. Dewa Sanzan is comprised of Mount Haguro, Mount Gassan, and Mount Yudono. There is a longstanding historical conflict between Buddhist-oriented…