In order to pay off her husband's debt, her wife Nanako decided to work at a hot spring inn deep in the mountains. Her husband's older sister, Reiko, hears guilt towards Nanako for shouldering her brother's debt, and hears rumors that the inn where Nanako works is dangerous, and heads to her inn. What Reiko sees there is Nanako's changed appearance, tied up in her restraints and writhing in madness. Reiko decides to give her own body in place of her Nanako. However, the feeling of the hemp rope biting into her crotch gradually drives her sister-in-law's reason out of order.
