There's iron dust in old wounds, in Kai's blood, and he thinks to warn Marco about it, that trying to do magic with it might actually hurt Marco too. But then he tells him to hush, and Kai frowns instead, ready to fuss about that. He's not a child, to be put into his place.

Instead he thinks back to Marco saying he can't change how he reacts to Kai, and the way that even under these circumstances there's a certain calmness that takes him over when Marco touches him.

He fights that, too, because Kai is used to fighting. "Be careful," he says instead. "Don't need you incapacitating yourself." He's pretty sure Marco's guard wouldn't take kindly to that.