I'm not sure specifically which 'old canal chair story' you are referring to. There could be many stories related to an old canal and a chair. It might be a local legend about a chair found near an old canal, or perhaps a story about someone's experience sitting on a chair by the canal long ago.
The significance could be in its connection to the local history. It might represent a certain period when the canal was more active and the chair was part of the daily life around it.
Perhaps he just starts right in with the main event, like 'I was there when the big storm hit our town...' without much preamble. This gives a sense of urgency and immediacy to the story.
Through its appearance. If it's old and dilapidated, it might tell of years of use and the passage of time. For example, a chair with a broken leg might have a story of a wild party where someone accidentally broke it.
Well, a 'beach chair visual novel' is probably a visual novel where the beach chair is used as a motif. Visual novels are known for their strong visual elements, so the beach chair might be used to create a certain mood, perhaps a relaxing beach - like atmosphere. It could also be that the beach chair has a symbolic meaning within the story, for example, representing a place of rest or contemplation.