There is no specific story so it’s same as in pokemon crystal.

Pokémon: Crystal Version is the most up-to-date of Nintendo’s Pokémon games, but it isn’t exactly the sequel that fans have been anticipating. Similar to Pokémon Yellow and its Red/Blue brethren, Crystal is merely an update to the Gold and Silver versions that preceded it. As such, those already knee-deep in the Gold/Silver series won’t find much of interest in Pokémon Crystal