Certain "Promotion Cards" are exclusive to the 3DS version or unlocked via special DLC/QR codes. These are essential for performing high-tier like Heartful World .
: If you are playing on a non-Japanese 3DS, you may need a decrypted DLC file or custom firmware to access these additions, as the game was a Japan-exclusive release . Aikatsu Stars! My Special Appeal - Nintendo | Fandom
: Always install the base game first before applying the 122MB DLC package to ensure the internal file paths line up.
Can't install DLC because encrypted, but decrypt isn't working? : r/Citra