Ace is a playable character in the game, 20XX.
Ace is a melee fighter, starting off with the A-Saber, which attacks with a three-swing combo. All of Ace's weapons have enemy-piercing properties, and can attack certain parts of enemies which Nina cannot.
Unlike Nina, Ace's combos can delay boss invulnerability frames. Bosses take damage from an entire combo before starting their invulnerability frames, though hits after the first only deal 75% damage.