This is the first of your games that I think I've played! It's certainly short, but it didn't need to be any longer. The forest background is so pretty! The purple shadows fit the mood very well.
Based on how your afterword suggests that a happy interpretation is intended, I'm guessing that the black dog might be a spirit form of Mila, or came on Mila's behalf, to protect Hans and steer him out of the forest before nighttime. A nice day that he can carry with him, as long as he doesn't think about it too hard? It's sad seeing him just standing there talking to himself once the illusion is revealed... But I'm sure I'm still missing something!