Flash Step (フラッシュステップ, Furasshu Suteppu?) is a technique exclusive to Kingdom Hearts II Final Mix. It allows the user to unleash a guard-piercing attack on a slightly distant target while keeping up their own guard.
In Kingdom Hearts II Final Mix, Flash Step is an action ability exclusive to Sora. It costs 2 AP to equip. When equipped, Sora slides forward with his Keyblade held in front with both hands, before stopping with a small jump that brings the Keyblade upward. This allows him to break through an enemy's guard or parry their attack without his own attack being blocked or interrupted, dealing two hits. Physical defenses such as a Large Body's front notably do not stop the attack either. The range that would activate the attack begins at roughly the distance that Sora would deliver his basic thrust, to just short of the distance of Slide Dash.
Learning Flash Step
Kingdom Hearts II Final Mix