Okay, I couldn't resist. I heard this song, from Phantom of the Opera in case you didn't know, and just had to make a small little oneshot.
Zuko knew something was wrong with Katara. He didn't know how he knew, he just knew. It became obvious even to her idiot brother when she muttered something about taking a walk and leaving the campsite. Sokka knew better than to try and ask what was wrong, but Zuko didn't. He stood and followed her.
"Where did those two get off to?" Toph asked. Sokka shrugged.
"As long as that…Firebender doesn't harm my sister, he could jump in the river for all I cared." The fifteen-year-old warrior yawned then clambered into his sleeping bag. "Good night!"
Soft sobs reached the former prince's ears as he neared an outcropping of rocks. "Katara?" he called softly.
"Who's there?" He could tell he had frightened the Waterbender.
"It's only me." Zuko stepped closer and found Katara sitting on a rock. At first, she looked surprised, then relaxed.
"Oh. I thought it was Sokka or someone else," she muttered, sounding relieved. The prince didn't ask why she felt that way. He merely walked closer; Katara stood and fell into his embrace.
"What's wrong?" he murmured into his sweetheart's ear. The feel of Zuko's arms around her had caused Katara to sob harder.
"I'm just…scared, Zuko. What if something happens to Aang or Sokka or Toph or…you? What if you all died and I'm the only survivor?" Katara's body began to shake.
"There is no way that's going to happen, Katara. Aang is the Avatar, your brother is too stupid to die, and Toph is too stubborn," Zuko assured her.
"What about you?" Katara whispered. "I don't want to lose you, not now."
"I won't leave you, Katara. It took me too long to find you," he replied, stroking Katara's braid.
Slowly, Katara relaxed. "Zuko…?"
He brought her face up to meet his. "What?" Before she could answer, he closed the gap.
"Promise me that you won't leave me or push me away," Katara finished when they broke for air.
"I promise."