Final answer:
The author portrays Echigo as a remote place through detailed descriptions of inaccessible terrain and the reactions of its inhabitants to an outsider's presence.
Step-by-step explanation:
The author unfolds the idea that Echigo is a remote place by describing the protagonist's experience upon discovering an isolated and hidden plain surrounded by high and inaccessible mountains after passing through a huge stone door. This setting conveys a sense of remoteness and seclusion, effectively conveying Echigo as an out-of-the-way place. The surprise and hostility of the inhabitants towards the outsider reinforce this feeling of Echigo being cut off from the commonly traveled paths and areas inhabited by the majority of people.