Kotone Takashina, Mami Yuzuki and Yuuri Kanou are three high-school students members of the Mystery Club of their school looking for spooky events happening around. One day, after she discovered via Internet about a ruined place located in a forest near of their town, Kotone decide to check it with her friends. However, a sudden downpour take the three girls by surprise and instead of ruins, they discovered an European-styled mansion who belongs to a mysterious man and his young twin sisters. The man, Shuuya Houjou, allows them to stay inside of his house until the downpour ends, but the three girls will soon learn about the dreadful secret hidden inside of the mansion...