I'm not sure specifically as I haven't played it. But generally, a visual novel about a ghost on the rooftop might be about a story where the main character encounters a ghost on a rooftop. It could involve mystery, horror, or perhaps a more emotional story of the ghost's past.
Since it's a visual novel, 'ghost on the rooftop' probably tells a detailed story. The rooftop setting is often a place of isolation and mystery. The ghost could be a remnant of a past event, like an old tragedy. The visual novel might use this concept to explore themes such as death, regret, or unfulfilled desires. It may also have unique art styles and music to enhance the spooky atmosphere of the rooftop with the ghost.