S-4 isn't as good as Papyrus at keeping his magic under control. Emotions rise, and his eyes often betray him with sparks of colour and magic. He tries to keep it under control, even if it's not exactly dangerous... but in such a distressing situation, he can't help it.

As he gently touches the human's arm, green magic flickers along his fingerbones and towards the bruise, attempting to soothe and mend the skin. He keeps his worried gaze on Chara for any possible sign of pain.