[hodil]

The only thing i can make out of the paragraph below the Epitaph is that Nagasaki is involved. And the green route in the picture is related.

鮎の川とは線路のことであり、金蔵の故郷は長崎が一番可能性があると推測しました。

I think he meant that the green route is the sweet fish river.

And that Nagasaki was possibly the place of Kinzo's beloved hometown.