After accepting an invitation from a mysterious trainer, Ash, Misty and Brock meet Mewtwo, an artificially created Pokémon who wants to do battle.

This is the story of how Ash and Pikachu first met. At first, Pikachu was disobedient towards Ash, but Ash only wanted to be friends with Pikachu. On the day they set out from Pallet Town, both of them saw a Ho-Oh flying and they made a vow to meet it.