Player One
When selecting a character, make sure your cursor is on Akira. Press left to go to Jacky, then press right to go back to Akira. When repeating this process, you'll hear a countdown begining at 5. Keep going till you reach zero. Once you reach zero, Dural will now be playable.

Player Two
When selecting a character, make sure your cursor is on Jacky. Press right to go to Akira, then press left to go back to Jacky. When repeating this process, you'll hear a countdown begining at 5. Keep going till you reach zero. Once you reach zero, Dural will now be playable.