Takashina Kotone, Yuzuki Mami and Kanou Yuuri are three high-school students who belong to the Mystery Club of their school and are looking for spooky events happening around. One day, after reading through Internet about a ruined place located in the forest close to their town, Kotone decides to see it out of curiosity and brings Yuuri and Mami with her. However, a sudden downpour takes the three girls by surprise and instead of the excepted ruins, they discover a mansion where the owners are a mysterious man and his twin younger sisters. The owner, Houjou Shuuya, allows them to stay in his house until the downpour's end, but the three girls will soon learn about the dreadful secret that is hidden inside the mansion.