Pokémon Adventures, Vol. 6 (2nd Edition) by Hidenori Kusaka

Pokémon trainer Red has vanished! Yellow Caballero and Pikachu's search leads them to the mysterious headquarters of the Elite Four on Cerise Island. Who has the baddest Pokémon around? There's only one way to find out...! And watch out for Team Rocket, Pikachu... Are they your enemies or your allies now?