The airbender's response takes the wind out from Zuko's sails just by the first look. He feels his heart clench and drop into his stomach at the following words, as a dark expression sets in over his face. He'd gotten the same response from Iroh. Has he been a fool under her thumb all this time? Had he deluded himself into thinking he was being wise to be kindhearted, when he was being just as thick as usual, Azula four steps ahead as usual? He looks weary, himself.

"I understand," he says softly, eyes downcast in his lap. "I wish I could explain— I know what you're saying, what you must feel... And I can't prove anything for her. But— it was you and Uncle who taught me to believe in the power of second chances. Third chances. Even Azula deserves redemption; she's a person, not a monster... But I know that's hard to believe for anyone who doesn't know her that closely. Even for Uncle. It used to be even for me. It's just— it's different, being spirited away. What's there to fight over here, away from everything else that matters? It's just us now, just us as people..."

This was the most honest case he's made in her favor so far. He'd been convicted in defending her against their uncle, feeling more gusto there, leaning on family ties. But Aang? There was nothing but Zuko's honesty to defend Azula.