Mii Fighter is a customizable playable character in the 'Dairantou Smash Bros.' (Super Smash Bros.) series. Players can create their own Mii Fighters, choosing from three classes: Brawler, Swordfighter, or Gunner, and personalize their appearance and moveset. Mii Fighter does not have a fixed personality or backstory, as they are designed to represent the player or any custom character. In the game, Mii Fighter allows for unique gameplay experiences and brings a personal touch to the roster.