Seriously, He Didn't
Zuko did not want Aang.
There was anything but static in the air between them, almost as tangible as the lightning that could've ended the both of them. It was anything but tempting to push Aang against the wall and force that smug smile off his face.
"You just don't want to admit I might be better at something than you," Aang teased, his shoulderblades just touching the wall behind him, his eyes alive with an invitation.
Zuko folded his arms across his chest and scowled. "Who was the kid who practically begged me to hold his fire for him, huh? Oh yeah," he leaned over Aang, "that was you."
"Yeah," Aang leaned up to him, unafraid, "and who was the kid who kicked your butt for almost half a year?" Something in his face changed and he jerked back, laughing kindly, the smug expression gone, and Zuko wilted, wondering when the past between them would die. "Just let me show you, okay? We can do it outside, if you're really so worried about your fancy hallway."
Without waiting for an answer, Aang turned and started to walk away, near imperceptible scorch marks trailing after his fingers on the wall. Zuko sighed. "It's not the hallway I'm worried about." Nevertheless, he followed, his eyes tracing Aang's back.
Outside, Aang walked backwards, smiling at Zuko. "D'you wanna be my test subject, or would you rather a servant?" he asked, the mischievous quirk back in his lips, his shoulders curling in slightly.
"I think the Fire Lord can prevent himself from being burned, even by a wayward Avatar," Zuko replied haughtily, brushing invisible ash off his shoulders and tilting his head up. Aang chuckled, and Zuko repressed a smile.
"Okay, okay. Just…" Aang glanced around the courtyard and moved to an area where trees didn't overhang. "Okay. Here." He pointed in front of himself, and Zuko obliged to stand there, watching Aang warily. "Sit," he commanded.
Zuko nervously surveyed the ground and frowned at Aang. "Are you sure-"
"Just trust me!" Aang insisted, twirling his fingers and flicking air at Zuko. "It's really cool. Sit."
With a sigh, Zuko complied, folding his legs and staring up at Aang. He supposed he had no other choice.
The moment he sat, Aang shifted into a stance, arms lifted, sobering. His eyes drilled into Zuko's and though he knew this was still Aang, there was something so inherently different and serious and Avatar that he couldn't stop the goosebumps from rising on his arms. Then Aang's arms fell, and Zuko stopped thinking.
It felt like every nerve was opened up and charged with heat or something more, and it wasn't electricity, but Zuko's body jerked as if it was. His back arched, his mouth falling open, and smoke fell out of his mouth and nose. "Aang," he started to say, but the smoke was replaced with fire when he tried to breathe out, and then his nerves closed and it stopped, but his body was still alive. The smell of something burning filled his nose but he didn't care, because he was energy.
The grass underneath him burned.
Aang smiled, satisfied and unafraid, watching as Zuko shuddered, brimming with fire and blinking rapidly. He didn't seem angry, though his fists kept clenching and unclenching. "Zuko," Aang said, his voice low and forceful. "Focus, Zuko."
Zuko looked at Aang and stood up, sweeping a circle of fire around them because he could. "When does it stop?" he asked, clenching and unclenching his fists, killing the fire before it ran out of control. Then, "Can I do this to myself?" But then questions didn't matter any more, because Aang was smirking at him, hands shoved in his pockets, and Zuko wanted to remind Aang who was the Fire Lord and whose palace he was in.
"It'll stop in about a minute," he managed, before Zuko jerked him into a kiss and his words were muffled in Zuko's mouth.
Aang stumbled back, but Zuko caught him. "You moron," Zuko kept repeating against Aang's lips, cheeks, neck, and Aang breathed out the smoke Zuko breathed into him and tried to make sure Zuko didn't burn him.
"Zuko, calm down – you don't," Zuko kissed his lips again and held Aang's hands still. When he moved, Aang tried to continue. "You don't mean – ow," Zuko's fingers were suddenly digging into his wrists, his mouth still against Aang's jaw, "ow, ow," Zuko slowly leaned back, glaring at Aang, "OW, Zuko, ow, ow!"
"What was that?" Zuko demanded, his voice tense but controlled, and Aang nervously smiled at Zuko and tried to pull back.
"I just – I told you, I could heighten someone's energy, Zuko, that's never happened before. Really!" Zuko released his hands and Aang staggered back, panting slightly, face flushing darker the longer they stared at each other. "It's, uh, a firebending technique," he continued, rubbing the back of his neck. "Sorta – sorta like inverse firebending."
Zuko covered his face and inhaled, slow and calm and as deep as he possibly could, wishing he could burrow into his hands. "I didn't just do that," he said. "I didn't just do that," he repeated in a higher pitch. "Seriously. I didn't."
"Yeah!" Aang laughed, his voice higher than it should've been. "Yup, nothing just happened here. Uh – well, yeah, I told you it was neat, so um, maybe you can ask Iroh about it or something, I told – um, Katara – that I'd, uh, see her, so um," he edged around Zuko, "I'll see you tomorrow or whenever I see you next, okay? Bye!" He hurried back into the palace, mind racing.
Zuko groaned and sat down. "I did not just do that."
And Aang did not want Zuko to do that again.