Pokémon the Movie: I Choose You! is available in: French European Spanish Portuguese Polish English [Original] on Netflix UK
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.
When Ash tries to pick his first Pokémon on his birthday, he ends up with a stubborn Pikachu and they embark on a journey to find the legendary Ho-Oh.