Which Pokémon games introduced the Johto region and first launched in Japan on November 21, 1999?

Pokémon Gold and Silver introduced the Johto region and launched in Japan on November 21, 1999.

Developed by Game Freak and published by Nintendo, the games followed Pokémon Red, Green, Blue, and Yellow. They added 100 new Pokémon, bringing the Pokédex total from 151 to 251, and expanded the world beyond the original Kanto setting.

Gold and Silver also introduced the day-and-night cycle, Pokémon breeding, held items, and two new types: Dark and Steel. Players could eventually return to Kanto after completing the Johto storyline, a feature that helped make the games feel like a substantial continuation rather than a simple sequel.