The DLC files themselves contain Japanese text strings, voice callouts (e.g., “Let’s go! Aikatsu!”), and outfit descriptions in Shift-JIS encoding. Even on a US 3DS, the game will display Japanese. There is no fan translation patch for the DLC menus—only for the base game’s UI (via a separate mod).
You might ask: If decryption removes region locks, why does "JP Exclusive" remain in the keyword? aikatsu my no1 stage dlc decrypted 3ds jp exclusive
If you want, I can:
Use FBI to install the decrypted .cia file. The DLC files themselves contain Japanese text strings,