In Hatano Town, a gruesome murder occurs 25 years after a similar case where police officer Togashi Hiroyuki's sister vanished. Togashi, now a community safety officer, and elite detective Yashiro Mahito from Tokyo investigate with hidden agendas. Togashi was once suspected in his sister's disappearance, while Yashiro harbors secret motives. Amidst mutual distrust, their probe faces obstacles: lost case files, Togashi's erratic behavior, and pressure from Yashiro's high-ranking police official father to halt the investigation. When university student Yanagi Mio — whom Togashi views as a daughter — disappears, Togashi gets arrested as the prime suspect. Is he truly the killer? Who's the real "monster"?