Where do I install it?
Can you do it with reference to this site?
https://bibouroku.net/windows-japaneseization
If you prefer an English site, you can use a search engine to find out how to install Japanese on your PC.
I have one request.
In the folder "Darkness-Kingdom_Ver1.10\www\audio\bgm", there are "city of beginnings.rpgmvo", "eastern cave.rpgmvo", "old house. rpgmvo", "snow mountain.rpgmvo", and "West Forest.rpgmvo". May I confirm the names of these music data?
I expect these files are garbled.
In that case, I am sorry to make you wait again, but I will fix it again.