I know that if you select a Pikachu as your buddy and you walk 10km with it, Pikachu will swap from standing next to you to riding on your shoulder.
But is this effect accumulative, persistent and consistent?
For instance if I walk 5km with it, swap to another and then back to Pikachu for another 5km will it start riding on the shoulder?
What if I've walk 10km with it and it goes on my shoulder and I then swap to another Pokemon and back to Pikachu will it still be on my shoulder?
What if Pikachu is riding on my shoulder and I swap to a different Pikachu? Does the new one continue riding on the shoulder?