You can control Toguro 100% the last boss of the game. After you choose Toguro and after the AI/your opponent chooses a character, the screen will show your portrait, the VS logo and your opponent's portrait before the fight starts. Hold B, press Down, Down, Up, Up, Right, Left, and then release B. Press Select. You will hear a "Beep!" sound; if not, do the code again.
You will now start the combat with Toguro 100%!