Katara doesn't expect to find anything of interest in the boys' swordsmanship. She's watched Sokka train before, but Zuko's technique is unlike anything she's seen. His blades never meet, yet they move as one.
It almost looks like bending.
Katara has no need for weapons while she has command over her element, but watching Zuko, she remembers when her bending failed her. All the times a weapon would have done her good.
After dark, when Zuko is sleeping, she creeps into his room and steals his swords.
If it's as much like bending as it seems, she can teach herself.
Zuko isn't surprised to hear rustling in his room. Privacy is an unknown concept at the temple.
But he doesn't expect the blur of blue and brown at his door. Toph or Aang, he would understand. But Katara doesn't seem the type to snoop. Or at least to be caught snooping.
Zuko finds her on the terrace, swinging his swords like they are ropes of water. For a beginner, she could be much worse.
"I could show you some things if you want."
She starts and one of the blades clatters to the ground.
After a long moment, she nods.