NOTE: This chapter isn't smutty, but it will be starting next chapter. I just wanted to get their relationship off to a nice start.
The fire crackled gently as Sokka stared at the stars dappling the sky. The day had been long, but he wasn't tired. He heard shuffling coming from his right and sat up. Zuko's silhouette was visible, acing in circles around his sleeping bag. Sokka was bored and decided to get up and go see what he was up to. He tiptoed around to Zuko and tapped him on the shoulder. Then a fist met him in the face.
When he came to, Zuko was standing over hi, gently tapping his face. "Sokka? Sokka!" He whispered, trying not to wake the others. "Are you OK? I'm so sorry."
"I'm fine." Sokka sat up and his head swam. "Or maybe not." Zuko got some water from his bag and handed it to Sokka, fearing he had given him a concussion.
"I'm so sorry Sokka, I thought you were-"
"Hey. It's fine. I shouldn't have snuck up like that." There was a moment of silence broken only by the gentle crackle of the fire. Then, Zuko spoke.
"Um, what did you want to talk about?" Zuko's head was swimming with all the possibilities of what he could have done wrong. But that wasn't why Sokka was here.
"I just wanted to talk to you. Like a friend." Zuko wasn't expecting that. Friend? Really? "I don't understand why Katara is so angry. Our mother's death wasn't your fault. Just because you can make fire appear out of your hands doesn't make you inherently evil. You're a cool guy." Zuko hesitated before speaking.
"That's not how firebending works. The flames don't just appear." Sokka laughed and a warm feeling started to spread in his chest. Was this what family was like?
They talked for hours till the sun rose, laughing and sharing stories of mean sisters and strange animals.
Over the next few weeks, Zuko became a member of the Gaang and felt truly at home. Katara had finally warmed up to him and Aang was treating him like an old friend. And he and Sokka would have long conversations every night. But feelings for Sokka started to arise, and Zuko feared that they weren't merely platonic.