With Mion's name clearly printed among the names of those killed in Hinamizawa twenty years ago, suspicion for Takumi's murder falls on her. But Mion isn't th eonly one whose story doesn't quite add up. How did the killer know Otobe's phone was the only one with a signal? How could Otobe's friends have simply "disappeared"? Is it really the work of demons, or is there a murderer among them?