In the 'Avatar The Last Airbender Avatar Kyoshi Novel', Kyoshi is the central character. She is the one with the Avatar powers and the one on a journey of growth. Then there's Yun. He is a character who has his own story arc that intersects with Kyoshi's in interesting ways. And Hei - Ran, an important figure in Kyoshi's life, who imparts wisdom and training to her.
There are several important characters. Aang is the central figure. He's the one who has to bring balance. Katara is crucial as she's not only a waterbender but also a great friend and support to Aang. Sokka may not be a bender, but his intelligence and skills are valuable. Prince Zuko has a complex character arc. He starts as an antagonist trying to capture Aang for his own redemption in the eyes of his father, but later he changes. Also, Toph, the earthbender, is an important addition later in the story as she helps Aang with his earthbending training.
Zuko is extremely popular as well. His complex character arc, from being a villain - like figure to a hero, is very engaging. People love to see his transformation and how he overcomes his inner demons and the expectations of his family and nation.
Katara is another important character. She is a waterbender from the Southern Water Tribe. She is brave and often serves as a moral compass for the group. She also helps Aang in his waterbending training.
Avatar: The Last Airbender is indeed an original story. It has its own distinct style and narrative that sets it apart. The combination of elements like bending powers, diverse characters, and complex story arcs make it a one-of-a-kind creation.