Hello, the Pokemon font does not support Korean characters. You'll have to change it to something that does support Korean glyph.
In the Fonts folder you have a font called PokemonDS and one called PowerGreenSmall. PokemonDS is used for most of the text and PowerGreenSmall is used for Battle UI (pokemon name, level etc...).
You can add new files to that folder or replace some of the existing files with another file.
If you add new files, you need to update Data/project_identity.yml (will be easier with Studio in the future but for now you have to use this file).
In this file you'll see PokemonDS and PowerGreenSmall, replace them by the name of the fonts you want to use.
Since only PokemonDS supports Pokémon number, you need to set the supports_pokemon_number field to false.
