At times, he doesn't even know why he takes the time to watch her...he doesn't know why he enjoys watching Katara in general.
He has his kingdom on his shoulders now and the crown within his hands, and Mai staying with him on a weekly basis.
He also knows she's engaged to the Avatar, who's his friend instead of his enemy now that the quest is over. But that hardly has anything to do with the harmless, silent appreciation he carries for her. It isn't anything negative or overwhelming, or even sinful. Most people have a favorite flavor of tea, others have a favorite poem or lullaby after all. That's all it is—one of his favorite things has become watching her work with the water, the way her dark fingertips play with the petals of the pond lotuses floating around in the fountains, the way she allows her passion to glow behind her eyes. He's also comforted by how she understands his lingering pain, for she has experienced the same type of tragedy in her past that he has. Their mothers gone, their Nations in distress, their futures unclear, both their hearts were splintered because of it. She understands the bonds between a brother and a sister, and knows just how delicate or breakable they can be if not nurtured correctly—how his sister betrayed those sibling bonds. She's shown him that he isn't alone in his grief, because she says it's normal to miss the ones they've lost rather unexpectedly.
And this cluster of familiar little details about her can calm him, and make him feel more at ease with himself. Above all, she makes him feel safe.
She loves those closest to her so fiercely, and she lets her thoughts be known, and lets her heart be heard, and most days she isn't afraid of that. This is what makes her beautiful. He can see this, almost like in a way that an artist would perhaps admire a masterpiece.
She is one of a kind among a sea of plain people and he hopes for her sake, this will never change. If it did, he would have to hold his tongue between his teeth, but he honestly would miss this Katara who laughs with them and teases him without fear.
Today she and her brother are visiting him at the palace during their annual journey home.
And as a fresh Fire Lord, who's still getting adjusted to the real importance of the title, Zuko still tries to be a good royal hostess when they arrive, offering them a tour of the newest instalments in the kingdom and a grand feast for afterwards.
Hour later, with a stomach filled with the Fire Nation's finest, Sokka happens to doze off in a chair, strained from the all the excitement.
Zuko, meanwhile, continues conversing with Katara, catching up on the latest news on the outside as he shows her the Imperial Gardens fully in bloom. The sight soon encourages her to provide him more insight on how to manage the streams running under the bridge, how to keep it clean and bluer.
Nodding in thanks, he escorts her the art gallery then, and they move together as a smooth flurry of scarlet and icy blue robes.
Katara is already studying an old painting plastered on the wall when the nameless servant posted at the doorway gazes at his lord for a bit longer than he probably should have...
Zuko turns his head away from him, saying briskly, "You may go."
The servant immediately blinks out of his trance, appearing both horrified and flustered by his own carelessness and he bows at them quickly before scurrying out of sight.
Moments pass before Zuko notices her wandering back up to his side, flashing him a small cunning smile. "You really shouldn't let it bother you anymore. Just don't try to hide it every time someone looks at you that way."
"Why not?"
Her hand lifts to touch his scar, which summons up memories of the night in the cave crystals in his mind.
"Because," she adds simply, "It is what makes you one of a kind."