Question: how do you get mega stones in pokemon let's go?
Answer: The Pokémon trainer Blue is seen throughout the game, but he appears once again after you win your 7th Gym Badge on Cinnabar Island. This is when he explains Mega Evolution to you. He then gives you the Key Stone as well as the Mega Stones for Venusaur, Blastoise, and Charizard X and Y.