Having lost her mother a few months prior, Yura Michiru, now completely alone in the world, was taken in by her mother's sister, the Saegusa family. There, she met her kind cousin, Mika, who attended the same high school. The three of them—Michiru, Mika, and Miya's boyfriend, Shingo Kawai—quickly became close friends. One day, just before summer vacation, Michiru and Mika saw the ghost of a girl in a sailor uniform. From that day on, the balance between the three of them gradually began to crumble. Mika began to suspect the relationship between Michiru and Shingo, and started to treat Michiru harshly, as if possessed by something...