The story begins when Kazuno receives a letter from an old friend. The letter says that ever since a group of them tested their courage at an abandoned ruin, a series of strange and disturbing events has begun to occur. Half out of curiosity as part of her research, Kazuno visits the people involved. However, what awaits her is only the beginning of days filled with terror that will eventually consume her as well. One of them dies under mysterious circumstances, and the remaining survivors gradually begin to lose their sanity.