I had to grin when I read this prompt, since I'm currently writing a fake dating Zutara story. So, the following will be a future situation from that story, set in the same AU.

Day 10: Fake Dating

They had decided that they would need to practise to act like a couple to convince everyone that they were indeed one.

Katara wished they didn't have to do that, but Zuko was such a bad liar and such a bad actor that they would definitely need the practice. She just hoped she wouldn't throw up during kissing practice.

It's not like she didn't find Zuko handsome. He definitely was, but she just didn't feel attracted to him. He looked way too much like some posh snob, and that combed back hair was an absolute no-go. Other than that, she found he had a nice face and nice lips, now that she was looking at them.

They were sitting on her bed in her tiny one-room-apartment, trying to get comfortable for kissing practice. If Zuko hadn't been quite physically affectionate with his ex in public, this would also not be necessary. But it would look strange, if Zuko would not act with Katara like that in public.

Katara waited for him to lean in, but she noticed that he was way too tense to do that. If she touched him in the wrong spot, he would probably shatter into pieces.

She really had to do everything on her own, since relying on a guy never worked.

So, taking a deep breath, she leaned in, supporting her weight on her hands, which were placed on her mattress.

She saw Zuko's eyes widening, as he swallowed.

"Try to relax," she said and closed the last bit of distance between their lips.

When they touched, it felt normal. Katara was just glad that she didn't feel disgusted, since she didn't want to make Zuko feel bad.

His lips were warm, dry and soft, perfectly kissable. Letting out air through her nose, Katara closed her eyes and pressed her lips firmer to his.

She tried not to think too much about the weirdness of the situation, but more about the fact that she was kissing a handsome young man. She could try to enjoy it. She never kissed anyone who she didn't have feelings for, but it was definitely worth trying.

She hadn't kissed anyone for more than six months, and she hoped this kiss would sate that need a bit.

But Zuko didn't move at all.

Retreating a bit, she looked at him worryingly. "You would have to kiss me back, you know."
She almost missed it, but it looked like his head had followed her retreat a bit. He blinked, then rasped: "Yeah, sorry, I'm gonna do that now."

He still didn't move, and she finally understood that he waited for permission. So she nodded.

The first contact of their lips was soft again, trying to get used to these unknown pair of lips.

A spark of electricity shot through Katara, when Zuko tilted his head and moved his lips against hers.

Oh, that felt good.

She leaned closer to him, followed the movements of his lips, strengthened the pressure on his mouth. He answered with slightly faster movements, opening his mouth.

That made her take in a sharp breath, and she wondered if they should try to get this far. They hadn't talked before about tongue kisses or normal kisses. Just about kisses. But maybe it was obvious that those had to be tongue kisses. She had no idea, and she felt herself panic a little bit.

Maybe she should just try it.

She touched his lower lip with her tongue, slowly, and licked it, making him taking a sharp breath. So maybe she had surprised him.

But he didn't back away, but answered with his own tongue stroking her lips. They tingled at his touch, which felt very good, and Katara overcame the urge to shove her hands into his hair and to pull him closer.

The electricity spread from her spine to her chest and stomach, making her feel fluttery and warm inside. If they kept doing this, she would definitely get aroused.

Pressing her eyes closed, she touched his tongue one last time and drew back, slightly out of breath.

Zuko's eyes were closed, and his cheeks were flushed.

She took his expression in, feeling surprised and somehow pleased. So he had liked kissing her. If he had thought about touching her, too?

Blushing, she quickly looked away, but heard him swallow.

"Uh, that wasn't bad," Zuko said, sounding so awkward that she had to cringe. "Good practice," he murmured.

"Yeah," she agreed. "It will suffice, won't it?"

He shrugged. "I'm not so sure. I didn't even dare nearing you in the beginning."

"Mhm." Forcing herself to look back at him, she blinked. "You could also tilt your head in the other direction. My neck got a bit stiff."

"Oh." She saw him blushing again. "Sorry. I found you were a bit reluctant, though."

"So… try again?" She raised her eyebrows, trying to seem as if this was not embarrassing at all. And as if she didn't want to kiss him again.

"Yeah."