A/N: Prequel to The Phantom.
Zuko can hear Katara cursing and the sound of someone hacking into wood.
Therefore, he knows that she must be practicing.
They've turned one of their private gardens into a training area. It wouldn't do for the servants to be spreading rumors about how their new Fire Lady has expressed interest in learning how to sword fight out of nowhere.
Zuko steps out of the shadows and Katara slips into view. Her hair is down, she's covered in sweat and her cheeks are pink with rage.
"Everything all right?" he calls out tentatively, holding out his hands and stepping up to her. She whirls around, clearly taken by surprise; Zuko jumps back as the blade nearly skims his neck.
"Uh, careful." He rubs at the nearly cut skin subconsciously. "It wouldn't look good if you were to slice open your husband's throat three months into marriage."
"Shut up," she growls, chest heaving.
"How's your practicing coming along? Are you ready for our lesson?"
Katara straightens her back and wipes the back of her hand across her forehead. She looks so tired already. "Zuko…" her voice is bleary. "I wasn't expecting taking your place to be…this hard."
"Well, you don't have—"
"We both know that I have to. It's just that I'm no good at this. How am I going to master two swords if I can barely handle one?"
"I think you've got potential."
Katara frowns, holding the sword up a bit. "How do you know?"
Zuko remembers how Katara could barely lift the sword a couple of weeks ago. "Well, for one thing, you can already hold your sword with one arm."
When Katara looks down and comprehends this, she smiles.