Last but not least, every brand new Poké Ball Plus comes with the Mythical Pokémon Mew inside. Currently, there is no other way to obtain a Mew in Let’s Go. For those wondering, you cannot transfer a Mew from Pokémon GO to Let’s Go, to get Mew that way.
To obtain Mew, you need to be playing the game with the Poké Ball Plus. You must also be connected to the Internet. Open the main menu and choose the Communications menu, then “Mystery Gift”. If done correctly, a “Get with a Poké Ball Plus” option should appear. Select this.
Your Mew will then be sent straight to your Pokémon Box. It will be Level 1 with a completely random Nature. Also, your game will be automatically saved after you receive Mew.