Expert mode
At the "How To Play" screen, press Left, Right, Left, Right(2), Left, Right, Left.

Play as Ryuji Yamazaki and the Jin twins
At the character selection screen, highlight the following characters (in order) and press X before moving on to the next person (a sound will be heard each time X is pressed): Terry, Hon Fu, Mai, Geese, Bob, Sokaku Mochizuki, Andy, France, Joe Higashi, and Blue Mary. If you entered the code correctly, the portrait for Ryuji and the Jin twins will appear on the character selection screen.