While Jack was fighting Ronald and Spring Crown on the mound atop the cave's entrance, Arthur was down there fighting the native soldiers.
Arthur's fighting style wasn't like Jack, who relied on speed to move around while fighting a mass of enemies. Arthur mostly stayed at the same spot. He only moved a little when needed, but none of the enemies were able to land a hit.
His katana slashed with lightning speed which knocked any attacks that came and delivered counter slash with equal speed. Each of his slashes was coupled with mana manipulation, thus resulting in high damage.
Arrows and single-target magic that came at him were slashed by his katana, even one from his blind spot.
