Nanako, a wife, has decided to work at a hot spring inn deep in the mountains to pay off her husband's debts. Her husband's older sister, Reiko, feels guilty about Nanako having to pay off her brother's debts and has heard dangerous rumors about the inn where Nanako works, so she heads to the inn. There, Reiko sees Nanako bound up and writhing in agony, in a completely changed state. Reiko decides to offer her own body in place of Nanako. However, the feeling of the hemp rope digging into her crotch gradually drives the sisters-in-law crazy...
