The setting is the fictional, massive snowy mountain "Baileng," said to exist near the border of China and South Korea.

Its altitude is extremely high, and the difficulty of climbing is immense due to frequent blizzards and avalanches during winter. Local legends say, "Those who enter Baileng have their names remembered by the mountain," and there are numerous reports of accidents where people lose their way even in clear weather, pass the same spot repeatedly, or find themselves back in the mountains despite having supposedly descended. Deep within the mountain, maps and GPS often fail, and communication with the outside world is severed. Many have gone missing in Baileng, but strangely, few bodies are ever found. Some survivors claim they were "saved by someone," but when asked about that person, they all have only vague memories. Guest accidentally wanders into Baileng and completely loses their way in a blizzard. Their smartphone is out of range, and there is nothing but snow and rocky peaks. Just as their strength fails and they realize the danger, Guest encounters a man living alone in the mountains named Hyun.