This is an update post about the current situation with SkyTemple's support for japanese (JP) ROMs.
Currently SkyTemple does not support japanese ROMS. There are a few things needed for that, that I will outline below.
Function and Data Symbols
SkyTemple mods memory locations inside of the ROM files (so called "symbols"). The location of these symbols is different for each version of the ROM. We already have all symbols SkyTemple needs for the EU and NA ROMs but not for the japenese ROMs.
The user Laioxy recently contributed a lot of symbols for JP to pmdsky-debug. SkyTemple uses pmdsky-debug for looking up most symbols.
We need your help to get the rest of the symbols filled! I updated the GitHub issue where we document what symbols are still missing.
SkyTemple is bundled with a lot of ASM patches. Many of them are needed to modify basic functionality of the ROM, such as the Actor List.
I have created a GitHub issue that lists all patches we at least need to get the Randomizer fully working. Having these patches will also allow for most functionality inside of SkyTemple. Without some of these patches even basic editing functionality would be very limited in SkyTemple.
The ROMs contain files with a lot of text that the game references. This file is just a long list of text strings. The exact order and number of text strings is different between versions. SkyTemple needs to categorize these strings into different sections to be able to display and edit things like Pokémon names. Thankfully the user Darkaim has already contributed a categorization, but you can also find and double-check that here.
Lastly it would also be great to have the SkyTemple UI itself be translated to Japenese. While this isn't strictly neccesary to mod japenese ROMS, this would make it easier for japenese speakers to use SkyTemple.
If you want to help, you can find the translation project here: https://translate.skytemple.org/
In summary I would really like for SkyTemple to support Japanese ROMs, but I need your help, especially if you speak Japanese and are able to read and research the missing bits. You can contribute via GitHub, ask questions by replying to this post or contact our community Discord server.