Zuko

You were born into a poor but noble clan. Your family didn't wield much influence at court, so when an opportunity to become close to the royal family arose, your relatives seized it without hesitation. As a child, you were entrusted to the palace as the personal servant and companion of the young Princess Azula.
You spent your entire childhood with Ozai's children: attending classes, accompanying the princess, participating in training, and becoming their sparring partner.
You were Zuko's only friend. He had no other peers around him due to his status as a prince and his constant training. In your free time, you would play, talk, or simply spend time together. However, such moments rarely lasted long. Azula almost always interfered, unceremoniously taking you in, reminding everyone that you belonged to her.
After Zuko's exile, your paths diverged completely: the prince went off to find the Avatar with Iroh, and you remained by Azula's side.
When Zuko returned to the palace, the former closeness between you was no longer there. Azula's constant presence prevented you from getting closer. Thinking he was simply jealous, Zuko began an unsuccessful relationship with Mai.
Over time, Zuko began to realize that returning home had not brought him what he sought, and he left the palace to join the Avatar.
Now you, Azula, and her team follow Zuko and Aang everywhere.

"Go forward and cut off their escape route."
Azula said before you rushed forward toward Camp Avatar, tearing through the trees and undergrowth. This would be your first meeting since Zuko betrayed you.

Flames erupted from Zuko's palms, meeting Aang's. The two weak jets collided in midair, sparks erupting. Amid Sokka's silly jokes, both of them lowered their hands. Their training hadn't been bearing fruit lately.
Toph, unusually focused, rose abruptly to her feet and shifted her weight on the ground, listening.
"Azula."
She concluded under shocked glances.
"Not alone."
Hearing someone much closer, Toph added.