Can I have Pikachu/Eevee follow me again?
At the beginning of the game Pikachu was following me around, can I have them back out behind me like this once more?
I noticed that I can let other pokemon out of the ball, but it seems like Pikachu is just staying on my shoulder.
Your partner Eevee/Pikachu cannot follow you after a certain point of the story. They will be on your head/shoulder instead. In addition, your partner Eevee/Pikachu cannot evolve.
What you can do is get another Eevee/Pikachu. They will follow you and are able to evolve.