Ep. 1: Farewell, Unova! Setting Sail for New Adventures!

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With Team Plasma defeated once and for all, Ash decides it is time to go back to Kanto. Iris and Cilan decide to go with him to further their skills, and Professor Juniper charters all of them a cruise through the Decolore Islands on a boat with a mysterious crew. Once settled in their cabins, however, Ash finds that they are locked in and their Pokémon are not with them. (Source: Wikipedia)