Haruka ni Aogi, Uruwashi no - While some might say the setting is unrealistic, the romances in the main school routes are very emotional and impactful even given their situations. Every path stands on its own in the main school routes (the redheads in the branch school routes have related routes), and there is a tight focus on the relationship from the moment of the path split, with the relationship being slow burn early on in all three cases.
Gin'iro Haruka
Hoshi Ori Yume Mirai
Edit: To clarify, the best place to look for VNs with actual romance (vs harem guy gets to choose anyone) is VNs made between 2004-2014. To be frank, most of the supposedly romance-heavy VNs that came out after that were relatively low quality. Tone Works VNs stand out as an exception, as all of them have extremely good romance from beginning to end.