When she was 17 years old, due to some mysterious event, Kyouko developed a condition that made her memory reset every time she falls asleep. Before her illness started, she was living somewhere abroad for unknown reasons. There, she once encountered Fumifusa Kondou, and helped him in some way. In her apartment, there is a message written on the ceiling that tells Kyouko her name and that she is a detective. She doesn't know who wrote the message or why. While doing her job as a detective, she encountered Yakusuke Kakushidate during his string of misfortune, and from then on, the two have run into each other many times.