Srry for the cutoff. You will need the following to randomize USUM with no cfw (there probably is another way with dumping your rom but I found a completely different way to do this by using a Pokémon ultra sun rom):
A 3ds with Homebrew (duh)
A windows computer, windows 10 would be the best
PK3DS build 286 (yes that specific build)
Hackingtoolkit9 V9 by Asia81
At least 4 gbs on your SD card
At least 12 gbs free on pc
And HxD hex editor
1) find a DECRYPTED rom of US or UM. (Make sure your link doesn’t say part one and part two of US or UM. Try to find a file that downloads the full rom on one file) Download your rom
2) take your Hackingtoolkit9 V9 and there will be a folder that says cleantool9, SetupUS, and HackingToolKit V9. Put your rom in that folder
3) Run the SetupUS and then install HackingToolKit9 V9 and then open HackingToolKit9 V9 and it will show a bunch of commands. What you want to do is type in d at the bottom. Then it will ask you what the decrypted rom is. (This is a good time to rename your US or UM rom to something easier to type. For example, if you have US just call it PKMNUS. There isn’t a specific thing you have to call your rom. Name it to something that’s easy to type) Type in the name of your rom, and it will extract your rom, when it’s done it will say extraction complete. You won’t be needing this program anymore.
4) you want to take the ExtractedRomFS and the ExtractedExeFS and put that into a knew folder. Now, the randomizing begins!!!
5) Take your 286 build of PK3DS (the reason I chose that build is because we can randomize everything except the pokemarts. All the things we can randomize are in the ExeFS and RomFS, and that’s it. We can’t edit the pokemarts because it’s in the CRO section, and you would need cfw to randomize the CRO.) You can randomize everything in this build except pokemarts. Once you randomize what you desire, got to the next step
6) In PK3DS, press the tools button, the press rebuild, then press RomFS. This will take some time, but once it’s done, it will say done. You want to name the RomFS into this
US: 001B5000.romfs
UM: 001B5100.romfs
For the exefs, go into the ExtractedExeFS folder, find the .code.bin, and rename in this order:
Rename .code into either 001B5000.bin or US or 001B5100.bin
Then take that .bin part and rename it to .code, and move it to your hand folder (if you don’t have one make one), and the exefs is good to go.
Take the 001B5000.romfs or 001B5100.romfs and run it through the HxD hex editor and then you want to select everything from 00000000 to 00000FF0 and nothing under that. Do not erase anything under 00000FF0. Either press the delete/backspace button on your keyboard or right click the selected code and press delete. Save the file, the move the file into the hans folder.
7) take the sd card, put it into your 3ds and access Homebrew however you do, and then find hans. Open it, and make sure the target selector is on either your cartridge of USUM or the digital version of USUM. Move the dpad to the left or right to scroll through your games and apps until you find USUM. Then press the A button
8) make sure your settings say this
Region: ———
Language: ——
FW Version spoof: No
N3DS CPU clock: 268Mhz
Code —> SD: yes
Romfs —> SD: yes
Save configuration: no
Scroll down and hit ok, give it 5 to 10 seconds, and if you did everything right, congrats!