Question: can pikachu evolve in let's go pikachu

Answer: No, The evolution mechanic from previous games returns in Let's Go, Pikachu! and Let's Go, Eevee!; however, the player's starting Pikachu or Eevee cannot evolve, like Pokémon Yellow. Only other Pokémon that the player has caught can evolve, including the ones of the same species of the partner Pokémon. Some features, like Pokémon breeding and HMs, will be absent from the games.