This one was actually a dream I had once. Turned out to be quite a good storyline.
Disclaimer: I don't own Avatar. As if I'd be that awesome.
A faded line
Attempting to appear more refined, Sokka picked up his cup delicately in his right hand. He held it under his nose for a few seconds and inhaled the scent of Iroh's fresh tea before taking a first sip. He obviously liked what he tasted because it wasn't long before he was pouring himself a refill. Aang took this as his cue to begin addressing his friends who were sat around the table with him. He cleared his throat, breaking the chatty atmosphere, and causing the others to look at him, ready to listen.
"I called you here, my old friends, for a reason." Aang said kindly. He then turned to Toph, who was sat to his left. She stared blankly at him. "Toph, you have to help train the benders in the Earth Kingdom. The Earth King asks for your skills specifically." Toph nodded, a little confused. Aang continued. "Zuko is of course busy with his official Firelordy business, so he's unavailable. Sokka, you and Katara need to go home and help the Southern Water Tribe become the magnificent city it's always meant to have been." Katara shook her head in defiance, and placed her cup on the table in front of her. She took his hand in hers, causing Sokka to huff slightly and return to his tea.
"We want to come with you, Aang. Our place is by your side." She said, smiling, her eyes sparkling with her brilliant shade of cobalt blue.
"I'm sorry Katara. This is something I need to do on my own." Aang whispered. His words seemed to hurt Katara a little. Her face dropped, disappointed. She sighed and nodded. In these four years since peace was declared in the world, Katara had figured that when Aang needed his own space for a while, even if he didn't necessarily want it, she would have to oblige.
"You better not be always for long, Twinkle Toes, 'cause when you come back we need to have that earthbending battle you keep promising on." Toph said, giving Aang a quick punch on the arm.
Later, Aang was preparing for his departure. Momo attempted to climb into Appa's saddle, only to be picked up by Aang and placed on Katara's shoulder. "Sorry buddy. You stay here." Aang said, patting the lemur's head. "You look after Katara for me, 'kay?" He said kindly. Momo replied with his usual lemur chatter, which seemed to be an agreement.
Aang turned to Katara, and noticed a small tear running down her cheek. He wiped it away with his hand, then hugged her tight, much to the annoyance of Momo, who disliked almost getting squashed onto Katara's shoulder. Releasing her from their hug, Aang smiled. "I'll only be a few days. I'll be back before you know it." He said gently, tucking a strand of hair behind her ear.
"Promise me you'll come back in one piece." She whispered, a worried tone in her voice. Aang leaned and kissed her forehead.
"Promise." He whispered.
Aang airbent himself onto Appa's head, and patted it gently. He took the reins in his hand, and taking one last look at Katara, he mouthed "Love you." She smiled, another tear running down her cheek. Aang returned her words of affection, then turned back to the sky, and with a "Yip yip," Appa was soaring into the burnt orange horizon. Katara was left standing on the balcony of Iroh's tea shop, where she and Aang had kissed four years before. She watched the man she loved become smaller and smaller in the sky before fading away completely out of sight.