Johto was introduced as the new region in Pokémon Gold and Silver.
The second-generation games were released in Japan in 1999 for the Game Boy Color. Johto is the main setting for the player’s journey, with new towns, Gym Leaders, routes, and Pokémon distinct from the first generation’s Kanto region.
Gold and Silver added 100 new Pokémon, raising the total from 151 to 251. They also introduced breeding, a day-and-night cycle, the Dark and Steel types, held items, and a more advanced connection between the game’s time and the real world.
After completing the Johto adventure, players can travel back to Kanto. This unusual post-game feature is one reason people sometimes answer Kanto when asked about Gold and Silver’s setting. Kanto is available in the games, but Johto is the new region associated with the second generation.