Satoshi receives an invitation from Professor Yukinari Ookido to attend the opening ceremony of Professor Sakuragi's lab in Vermillion City. During the ceremony, an alert notifies the professors about the appearance of a rare Pokémon in the city's harbor. Satoshi and fellow trainers rush to the area to find Lugia, a Legendary Pokémon fighting with other trainers. Satoshi observes the other trainers' tactics and decides to strike Lugia with Pikachu's Thunderbolt attack, but it flees. To Satoshi's surprise, he meets a boy named Gou who also leaped onto Lugia's back. They embark on a wild adventure across the seas together. Lugia eventually drops them off, and the duo bids farewell before returning to the Institute. Professor Sakuragi is impressed with their encounter and invites them to become his research partners. Thus, their journey begins, exploring multiple regions and encountering various new Pokémon, some of which have the ability to Gigantamax.