How does Pikachu riding on your shoulder work?

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?

Solution 1:

Any current progress you have towards a candy will be removed when you switch buddy Pokémon. But, if you walk 10km with Pikachu, switch your buddy, and then put Pikachu back as your buddy, it will still be on your shoulder, and the total distance will be the same as it was before the swap.

IMPORTANT: This does not apply for all Pikachu. I have one Pikachu who has been my buddy for 15.5km, but when I put my other Pikachu as my buddy, the total distance walked was "0.0km". In the same way, 1km walked with a Pidgey or Squirtle will not be added to your total distance walked for all Pidgey or Squirtle.

So the total distance is kept whether or not the Pokémon is your buddy, but does not apply for all of the same Pokémon. Hope this was helpful.

Solution 2:

When you switch Pokemon, you lose the progress toward the current candy you're looking for.

What you don't lose, though, is a record of the total distance you have walked with that Pokemon, which will continue to be stored and shown again if you select that Pokemon as your buddy (source: I did this after my first candy with a Pokemon, and my previous distance remained recorded).

Despite being sure of the above, I can't be as sure about this: my assumption would be that given the distance recorded remains linked to that Pokemon, the game will "remember" the status of each individual Pikachu.

(I realise this isn't 100% proof yet, but hopefully it goes some way to answering your question until someone does try it!)