The world of “Pokémon” is evolving with “Pokémon Horizons: The Series,” a show with two brand new protagonists after Ash Ketchum finally caught ’em all and became the very best, like no one ever was.

Now that he’s officially become the very best, like no one ever was, Ash Ketchum is heading into retirement. The long-running and perpetually 10 year-old star of the beloved “Pokémon” anime will exit ...