I do not own Avatar: The Last Airbender or the charaters in the story, EXCEPT for Juno, who was my own creation. Daydreaming during work has it's good points. I thought of Zuko's past and realized we don't know much about it and why Zhao hates his guts so much. So, I basically created my own answer. Hope you enjoy!
Words - past events.
Zuko sat in his room, meditating, as he felt the ship slow down to a halt. They were about to port in a island taken by the Fire Nation from the Earth Nation. Though Zuko was banished from his home by his own father, the Fire Lord Ozai, the particular island was not considered part of the Fire Nation, merely a claim. They had stopped there to rest, stock on supply, and hear news of their home land.
There was a single knock at his door before his uncle Iroh, ex-general to the Fire Nation army, popped his head inside his nephew's door.
"Zuko, the men are heading out into the village, why don't you join us," Iroh said with a smile. "It's a beautiful day."
"No, thank you," Zuko said in a hash whisper, keeping his eyes closed.
"Would you really prefer this dark room to the sunny outside?" Iroh asked, walking further in. Though there were candles, the room remained very dim with no windows. Zuko had his feather downed bed, his alter with mirror, and his walls were decorated with broad swords, shield, and a Fire Nation banister. The rest of the room was used mainly for Zuko's meditation.
"I do prefer this, so if you please," Zuko responded, his voice acknowledging his irritation.
"If it makes you happy," Iroh sighed as he opened the door again. "I'll bring you news from the outside if there's anything interesting." He left when he received no response.
Out in the village Iroh made his way through shops and restaurants, with a soldier or two to carry everything he bought, when he came across the two square where people were gathered around a bulletin tower with papers and posters.
"Wait here," he told his men as they passed by an antique shop. "I'll go see what's all the commotion."
When he managed to walk through the crowd he saw a poster declaring about the happenings of a rebel fire bending group called Fire Ants. Citizens of the Fire Nation who detested the war and the reasons and effects of it. They had so far dismantled three barracks where weapons were made and stored and had assassinated two generals, a commander, and messenger. The count was only four men and two women and yet they had caused so much damaged. Orders were to capture them and bring them to the Fire Lord, dead or alive. Beneath the poster were names of the traitors, but one in particular made Iroh's jaw drop and in a flash ran past his men towards the ship.
"Zuko!" He cried out as he reached the ship. He ran below deck into the corridor where the rooms were located and busted into Zuko's room. "Zuko!"
"What is it, uncle?" Zuko said, jumping to his feet. He rarely saw his uncle in a panic and it brought unsteady feelings in him.
"Fliers… in the town square…" Iroh tried to say, catching his breath from running such a distance. After he took a few deep breaths he explained what he read In the village.
"So what's the problem?" Zuko asked, knowing there was a good reason to Iroh's panic.
"One of the names," Iroh said sadly, "It was Juno."
"No," whispered Zuko. "Not our Juno."
"That's not a common name, Zuko," Iroh said as he watched his nephew sit on the floor in despair. "And you know as well as I do she would do something like this."
"Do you realize she could be killed!" Zuko yelled up at him. Iroh closed his eyes sadly as he lowered his head. Zuko sighed and placed his hands over his face as he thought back to his only friend his age as a child.
The rain poured harder as Zuko ran outside, tears mixing with the rain. It was a rare sight to see the ten year old prince outside by himself, though no one noticed him either way. He had been tricked by his younger sister, Azula, that their father wished to speak to him. His father had no intention of seeing his son and was very upset at the interruption of one of his meetings with a general. Fortunately his uncle Iroh came to rescue and explained that he gave Zuko wrong directions to retrieve something for him. Hurt by the betrayal of his sister, he ran outside as it was raining.
He sat in a ball underneath a statue, trying to calm himself when he sudden heard a shy, soft voice. A girl looked around the statue and looked at Zuko with sad curiosity. She looked as old as him, if not slightly younger.
"Who are you?" He asked as he lifted his head.
"My name's Juno," she said softly. She walked closer and Zuko could see her red dress clung to her body as it got wetter and wetter and her raven black hair was matted to her face, her bangs parted to the left side and placed in a high ponytail. "You're Zuko, aren't you?"
"Yes," Zuko whispered.
"What are you doing out here, Zuko?" She asked, her voice never raising.
"Why do you care?" Not meaning in a bad way, just curious, or so that was how Juno received it. "Besides, why are you out here?"
"I saw you from the window and I wanted to help if there was anything wrong," she said simply. Her words sunk and Zuko stared at her in wonder at how anyone would care about him enough to follow him in the rain.
She sat next to him as he told his story about his sister's lie to get him in trouble. They stayed outside for another moment, their heads leaning against each other as Zuko calmed down. They went in soaking, but smiling and laughing none the less. From that day forth they were inseparable, the closest friends anyone had seen in the palace.