Tell me if you've heard this one; A girl flees the scene after seeing her two best friends together. she ends up in an abandoned place where she meets a boy who cheers her up. she promises to be his friend. later she realizes the boy was a ghost or spirit and terrified runs from the abandoned place only to regret it and tries to apologize with tears in her eyes. only she can no longer go back.

don't know if it was a one-shot or series.
-two best friends could have been best friend and boy she had crush on.
-there were non-human looking spirits/ghosts in the place with the boy.

so if you know the title of this manga, please inform me what its called

Koi Tomurai?

I think it's the first story

"I've seen a look in dogs' eyes, a quickly vanishing look of amazed contempt, and I am convinced that basically dogs think humans are nuts." -John Steinbeck

ah so it is, thank you very much