Aww, this is cute. I read it every year or so. I remember reading a long time ago that people often carry a torch for a past lover or crush, whether be from high school into college, or college into adulthood. Those folks will probably never forget the person who was special to them. I think this oneshot captures that idea really nicely.
One detail that separates this from similar works is that Nakayama actually gets a GF in the future. She might be stuck, and her heart might still be confused, but she's moving forward, too. Not only does this make the story more realistic, it adds a layer of complexity beyond "haha lesbians sad." Great stuff.