Possibilities:
- Fox raises baby (Jungle Book, Princess Mononoke)
- Fox leaves baby and another creature comes
- Fox has to choose between baby and its own cubs
- We are in a magical world and these are not just foxes and babies but creatures of magic and imagination
- Reversal of fox and human: Fox goes through the forest finding interesting things, the climax is when he finds this baby, and comes back everyday to feed it. Then one day the baby is no longer there. He searches everywhere and puts up notices looking for this baby. He finds out it's been taken to a nearby orphanage and tries to free the baby. He succeeds, but at a great cost.Turns out the baby isn't really a baby but the next generation of the forest spirit. The current tree spirit thanks the Fox by making his spirit a part of the forest.