1. check if you have the aeskeydb.bin from part 3 of Plailect's guide in the root of you SD card or your files9 folder
2. copy the save file you wish to inject in to files9 folder and name it gbavc.sav
2. start the gba game that you wish to inject the save into
3. wait until the game reaches the title scren, then press home button and exit to 3ds home menu (do not power off the 3ds after this)
4. go into system settings
5. exit system settings using the touch screen (this will cause the 3ds to reboot), then quickly hold the button associated with decrpyt9 to boot it
6. go to sysnand settings and inject the gbavc.sav
If the above steps do not work, you can follow the steps below:
Required files:
Yggdra Union gba rom
Yggdra Union VC cia
Agbsave9 (requires python 3):
https://gbatemp.net/threads/pre-release-agbsave9-tool-to-extract-agb_firm-saves.410684/
Ultimate GBA VC Injector:
http://gbatemp.net/threads/release-ultimate-gba-vc-injector-for-3ds.438057/
1. Download both agbsave9 and gba vc injector
2. open up gba vc injector and load the Yggdra Union rom
3. the injector should be able to determine the save type of the rom. Note down the type (either SRAM, Flash or EEPROM)
4. close and reopen the gba injector. This time load the Yggdra cia then click next step.
5. note down the title id of the cia then add two zeros on either side of the id (e.g. if the title id is E123, then write down 00E12300)
6. in the agbsave9 zip there should be a folder called agb_inject
7. copy the save file you wish to inject into agb_inject folder and name it "yusave.sav" (without quotes)
8. double click gen_rom.py
9. for the save's name type "yusave.sav" (without quotes)
10. output cia type "yusave.cia" (without quotes)
11. for the save type, use the number corresponding to the save type you noted down in step 4 (SRAM = 0, Flash = 1, EEPROM = 2)
12. the title id is the one you wrote down in step 5, in this case it's 00E12300
13. now you should have a cia file in the agb_inject folder called yusave.cia
14. uninstall Yggdra Union game on your 3ds using via system settings then install the yusave.cia from step 13. You should have a gba game called test on the home menu
15. run the gba test game and wait until "AGB_FIRM save injector" appears. Then exit the game.
16. go into Ninteno 3DS/[random number folder]/[another random number folder]/title/0040000 folder on your 3ds sd card
17. find the folder with the same title id as the one you noted down in step 5 (in this example it's 00e12300)
18. copy the data folder inside the title id folder and place it somewhere safe
19. delete the test gba game and resinstall yggdra union cia
20. repeat steps 16 and 17
21. copy the data folder from step 18 into the title id folder again
your save file should be injected into the game