Luke wasn't the one who looked tense after the end of the battle. When he looked toward the others, they still were pointing their weapons toward the corpse… a single enemy withstood their attacks for several minutes. That enemy could have killed them in a single attack, so it was like they had defeated the incarnation of death itself. When Luke saw his mother running, he also got up and went to check his father, but the damage was only on his arms. Aside from that, he only had a few scratches.
"Burn that image on your brain, Luke," Mark said. "The image of your cool father dashing in a heroic manner to protect you. That is your final lesson."
"You are still speaking nonsense…" Luke said and then sighed. "Rina, if you would, please, heal him."