Original title: Poketto monsutâ: Serebî - Toki wo koeta deai

Ash Ketchum travels with his pet Pokémon Pikachu and other friends to an island to investigate an especially rare species of Pokémon, Celebi. With help from Diana and her grandmother, Ash manages to capture Celebi, and discovers that the creature has the power to travel through time.

https://www.imdb.com/title/tt0287635/