Kuroko’s group goes to a hot spring deep in the mountains, where all the land is owned by the wealthy Yamatsukami family. But right as the family is deciding the next heir, the third son is found murdered, and with the only bridge in and out of the area destroyed, the list of suspects is small. Cut off from the rest of the world, the family begins to whisper about a mysterious “Ayako,” and before long, another victim turns up... With no end to the grisly murders in sight, how will Kuroko solve this closed-room case?