Horou is a high school student, living with his parents. One day before his seventeenth birthday, his father says to him, "I have something important to tell you." On that night, he has a dream: he is surrounded by fire, and he and his parents get separated.... When he wakes up next morning, he receives a pen from his pet cat. Also, "his parents went missing twelve years ago." What's happened to him and his parents...?