i'm not sure =/ I don't have the Jpnver, but my cousin's BF said he paid a fair bit for the Jpn ver of 'A song for XX' back then with the special case...the OS ver is in a regular sized case~
Btw, check out the Ayu-mi-x database
http://database.ayu-mi-x.com/albums/asongforxx.html
the OBI is different in the Jpn ver...the OS ver says "A song for XX" in english on the side and on the back it's got a description instead of Ayu's legs...
i mean...the OS Ver hasa pretty thick booklet too, but it's jammed in the regular cd case lol~