You can use this
Atelier_PAK_Decrypt.zip (18 not 17) to unpack the files in the game. All the costumes and such are in PACK00_02, including a naked model (with NO nipples or genitalia) called pc00_nkd, that can be renamed to replace any other costume in the game.
As of right now, no one knows how to decrypt the G1T or GZ files, so we can't do much more than that.