The Mount Akakura Emergency Shelter Cabin is a survival cabin situated on the remote Mount Akakura. The cabin is a practical structure intended to ensure the survival of stranded humans for as long as possible. Accordingly, it is where the four survivors of the HAL 18 aeroplane crash reside throughout the novel; these survivors are Fuyukawa Kokoro, Yomogi Seiji, Mayuzumi Lin, and Kusuda Yuni.
The cabin plays host to not just the desperate struggle for survival on Mount Akakura, but also the mental struggles and clashes between its four occupants. Under an overwhelming fear of death, cramped living conditions, and dwindling survival supplies, the possibility of an unsavoury end looms ever closer. The leitmotif of the cabin is Chaining.