You may use any Mii character you want, however you must start with a Mii character that is at skill level ZERO for this event.
Begin the game and try to defeat as many opponents in a row as possible (meaning you must progress to the next level after each victory to move foward in the game). Your score is taken as your skill level achieved once you lose a match to an opponent. The game will add or subtract some points based on that match you just lost, and your final score is taken after these points are adjusted.
No pausing is allowed. No breaks in between opponents are allowed.