Zero: Tsukihami no Kamen

Ten years ago, a suspected serial killer has kidnapped five girls from a sanatorium located on Rogetsu Island in Japan. The detective Choshiro Kirishima eventually succeeded in pursuing the criminal and rescuing the girls. However, several years later, two of the girls died under mysterious circumstances. The three remaining girls - Ruka, Misaki, and Madoka - decide to return to the island to find...