The healing gauge is the feature that was first implemented in Power Instinct Matrimelee and has been a staple since. When the fighter is hit by attacks, a portion of this red meter will appear in the health bar. As long as the damaged fighter isn't attacked, health will gradually replenish over this bar until it's filled up. The more damaging the attack, the more of the healing bar will appear. Something of this sort was also featured in Rage of the Dragons, though it worked differently in that the damaged fighter would heal only when not in play.