Towering over the Kanto Plain, the sacred mountain oyama (literally, "Big Mountain") has loomed large over the religious landscape of early modern Japan. By the Edo period (1600-1868), the revered peak had undergone a transformation from secluded spiritual retreat to popular pilgrimage destination. Its status as a regional landmark among its devotees was boosted by its proximity to the shogunal capital and the wide appeal of its amalgamation of Buddhism,...