A woman named Kazuko (Kimura) who was guilty of a “serious crime” in the past, along with three of her friends. Those friends suddenly begin to die one by one. Kazuko learns that one of those deaths is somehow connected to Mamoru (Nakamura Aoi), her younger brother from whom she has been separated ever since their father disappeared 15 years earlier. Although Mamoru knows nothing of his sister, Kazuko is determined to find the killer in order to protect Mamoru and herself.