arc pulls himself away from arm, smiling when the other grins, too adorable for his heart (and sanity) to handle. so he confides in ruffling arm's hair affectionately, mumbling "take care of yourself, okay?"
arm scoffs, answering, "of course! i'll be taking care of myself! i'll take care of myself from you! if it happens again, i won't hesitate to scold you! or beat you up! so, prepare yourself, phi arc!"
or arc resents himself for hurting arm (when he promises himself he won't). but arm has too many good bones in him to ever hate arc.