To repay her husband's debt, wife Nanako ends up working at a hot spring inn deep in the mountains. Her husband's sister, Reiko, feels guilty about Nanako taking on the debt and hears dangerous rumors about the inn where Nanako works, leading her to go there. What she sees is Nanako's transformed figure, bound tightly and writhing in agony. Reiko decides to offer her own body in place of Nanako. However, the sensation of the hemp rope biting into her groin gradually drives the sisters-in-law mad…
