itch.io

drag the files from the english folder into the korean folder and it will ask you if you want to replace the files

It's been 2 years but a more in depth tutorial:
1. First download the Korean version, this one includes the exe file required to run the game

2. I recommend making a folder with a meaningful title as this is where all the game files will be stored when you "Extract All"

3. Extract all of the KOREAN into the folder

4. When you go to extract all in for the English version, extract them into the "data" folder which is in "www" WHICH IS IN "발베니의 생일파티" this last one is the main folder for all the game's content