Japanese CDs, and games that come on CDs have a piece of card wrapped around the spine of the case to carry the barcode, and RRP (if there is one), so this stuff doesn't have to be printed in the inlays. OK, so far, but why's this important? For some reason, collectors of import games place an enourmous value on this little piece of card, and don't consider a game complete unless it's included. Most other people just view them in the same light as those 'Includes the hit singles...' stickers, and throw them out with the shrinkwrap. Anyways, just incase you might ever consider selling your game onto one of these people, the easiest thing to do is lift the CD tray out of the box and stow the card under there. That way, you can prettend you don't care about that kind of stuff, and no one will be any the wiser. :)

Aparently, spine cards are called obi cards in Japan. Just incase you see that mentioned on a Japanese auction or whatever.