Kouichi Yamadera as mythical Pokémon Marshadow (the role marks Yamadera's 20th consecutive appearance in a Pokémon film)
Shoko Nakagawa as Nurse Joy (the role marks Nakagawa's 11th consecutive appearance in a Pokémon film)
Kanata Hongou as Sōji, a young trainer who is aiming to become a professor.
Shiori Satō as Makoto, an energetic and strong-minded trainer.
Arata Furuta as Bonjii, a researcher who has been chasing after the legendary Pokémon Ho-oh.
The film's plot tells the story of how Ash (Satoshi) and Pikachu came to know each other. Pikachu was not cooperative toward Ash, but Ash only wanted to be friends with Pikachu. On the day they set out from Pallet Town (Masara Town), both of them saw a Ho-oh flying and made a vow to someday go and meet it.
Satoshi Tajiri is credited with the original work. Pokémon movie director Kunihiko Yuyama is directing the film. Rica Matsumoto (voice of Satoshi) is performing the opening theme song "Mezase Pokémon Master: 20th Anniversary." Matsumoto's original "Mezase Pokémon Master" song was the first opening theme song for the first Pokémon television anime series. Asuca Hayashi is performing the film's ending theme song "Oración no Theme ~Tomo ni Arukou~" (Oración Theme: Walk Together). The song is based on Shinji Miyazaki's "Oración," an instrumental insert song in the 2007 Pokémon: The Rise of Darkrai film that the character Alice plays to calm Pokémon.