A special investigative unit called FCIN investigates real-life murders and disappearances by writing up fictional worlds you can enter with a special key. When one of the investigators is murdered by someone in one of these fictional worlds, a young woman named Midori gets caught up in the case.

Ayaka lives with roommates. One day, she is caught in the rain while waiting for her boyfriend when she happens upon an umbrella that had been thrown away. She picks it up but, after that, she is nowhere to be found.