I have already gotten a lot of feedback from this one, and thought I should make some comments on this story. More than I had in the notes at the end.
One thing I love to do is play with styles. And if one notices, there is not a single line of dialogue in the entire story. I was inspired by movies like "Stand By Me", and shows like "The Wonder Years". An older adult, looking back at their youth and things that happened. And their sometimes musing adult narration at things in the past when they were kids. What was said was not important, the important thing was their experiences and what happened. Not what was said.
If it helps, imagine somebody like Richard Dreyfuss or Daniel Stern actually narrating it. Or for the younger generation, Don Cheadle.
Also, ultimately what happened with Kim is not all that important. She did live, and had not died in some tragic accident. Maybe she met somebody else? Maybe she had an encounter that went past their rules and was ashamed after that? Maybe she just thought that a long distance relationship would not work? We all have people in our lives that simply "vanished" for one reason or another. That is simply life.
And in even "Stand By Me", at the end the narrator said that he had drifted away from his friends of that summer. One being later killed the week before and he had not seen him in "over ten years".
However, Kim is alive and well. And like Keith, has moved on and led her own life. And likely also looks back at those summers with fondness, maybe even wondering sometimes what had become of him in the years since then.
But the slightly bittersweet ending is also intended. Sometimes things are not all wrapped up in a bow at the end, with everything explained. That is simply how life is.