The Japanese version of Brawl Brothers is hidden inside the U.S. cart. To access it, wait until the white Jaleco screen appears then quickly press B, A, X, Y repeatedly. If you've done the trick correctly, you'll hear a strange noise and a black-and-white screen will appear. Press Start and another strange screen appears, press Down three times on your control pad, and then press Start. When the Option Screen appears, it will have the Japanese title in the background. Choose the type of game you want and then begin play, Japanese style.