Date: All I know as of yet is that the questioner has owned it on VHS.
Country of origin: Unknown, but the animation style supposedly isn't anime.
At the very beginning there's a prologue with two characters talking to each other, whom reminded the questioner to the depictions of Pan from Greek mythology. Their conversation is about the story that the viewer is about to see.
So, it's about an Asian adolescent heroine, who's village is suffering from a drought and the story has a happy ending with lots of rain.
There was a man in it, who later turned out to be a dragon. Another element might be a treasure cave.
It's not one of the Nezha movies and not Taro the Dragon Boy.
(Unimportant side note: Trying to find this, I've stumbled upon 2 different threads on the net, both many years old, where people looked for this, but none of them got good answers, so this might be an elusive one.)