A 'under the bridge visual novel' could potentially revolve around the lives of the people who frequent the area under the bridge. It could be about their struggles, their relationships, or their dreams. For example, it might tell the story of a homeless person who finds solace under the bridge and the people they meet along the way. It could also be a love story set against the backdrop of this rather unique location.
You could try looking on popular digital game platforms like Steam. They often have a wide variety of visual novels available for purchase or download.
The location under the bridge could be a place of isolation. It might signify that the girl is in a marginalized situation, away from the normal hustle and bustle of society.
I'm not sure as I haven't read this novel specifically. But it could potentially be about the lives of people who are associated with the area under the bridge, like homeless people or those on the fringes of society.
I don't know as I haven't read it. It could be a group of misfits who gather under the bridge, like a young runaway, an old storyteller, and a street artist.