All I know is that you go to
www.bandainamcogames.co.jp/cs_support/enq and click the Gears of Destiny link. On the following page there's a text field where you're supposed to type in the code that's on the back of the game's instruction booklet. I'm guessing from there another page will appear with a survey. Have Google translate handy to help you fill it out. I think once you do it'll give you a code that use you to get the costumes from PSN.