In my citra only have open extra data and update file location, and there is no open mods location optionTo work on Citra, you do this:
1 - Download the patch CIA (Page 1) and extract it.
2 - Open Citra.
3 - Right click on Monster Hunter Stories (jp) game icon and click on Open Mods Location.
4 - Paste the files: romfs and code inside the 000400000016E100 folder.
5 - Done.