Kyuuyaku Mother Ghoul

A class from an all-girls Christian school are stranded on what seems to be an uninhabited island after a shipwreck. The most admired girl in class, Shouko, keeps everyone's spirits up, while several of the others, including anti-social Torino and her friend Hina, begin to explore. The girls soon find evidence that they are neither alone nor safe on the island... (Source: MangaHelpers)