Office lady Aya Mizuki had been suffering from chronic lower back pain, so on her boss's recommendation, she began visiting a clinic near the station. Her first electrical therapy session relieved her pain, prompting her to continue treatment. However, one day she was suddenly struck by intense pain at home and rushed to the hospital, only to find the corrupt clinic director and a nurse waiting for her. Excited by the sight of her suffering, they began escalating the treatment into something far more perverse. In the hospital's basement was a device Aya herself had unknowingly designed—used to torment countless women before her. And in that same basement, another woman was already trapped.