In the manga, the quoted sentence above is shown with an image of deserted road, and I guess the meaning should be something like this:
「I'm walking down the road, but not a single person in sight.. 」
But without the picture, I would have mistaken it as:
「I'm walking down the road, but so many people in sight.. 」
Please help me understand the grammar of the sentence, because to me it seems like a positive sentence.