It used to be on Fakku, the description simply: "Caution: Sadness", and it was the most recent one in the "catgirl" section before Fakku purged their library of all its old content and became a paysite with all-new content.
The young male protagonist finds himself trapped on a mountain on a snowy night and finds a cabin where there is a naked long-brown-haired teenager-looking catgirl who has sex with him. The next day, it's revealed that the catgirl was actually the long-dead ghost of the pet cat of the owner of the cabin who died waiting for him to come back home and it's implied that a ) her owner also died too on the mountain and b ) that the protagonist was actually the secret reincarnation of her long-dead owner (ala Spice and Wolf), who had now come back to her at long last. I can't remember the ending anymore, if she went to Heaven after that though or whatever.