|"Don't worry. I'm not a tattletale."|
|— On Ji talking to Aang.|
On Ji was a young student at a school in the Fire Nation. Her parents valued her education and hoped that she would succeed in school. They wished for her to further her studies at a good university in the Fire Nation Capital, where she could meet royalty and make the perfect Fire Nation wife.
Aang, under the alias of Kuzon, came to the Fire Nation school, claiming to be a new student from the Fire Nation colonies. After school ended for the day, Aang met On Ji, who noticed Momo hiding under his shirt and warned him to keep it hidden, thinking it was a monkey. Her self-proclaimed boyfriend, Hide, seeing "Kuzon" and On Ji together, stopped by and made it clear to Aang that she was his "girlfriend" by starting a brief confrontation, during which On Ji rolled her eyes, hinting that she was not particularly affectionate toward Hide. Later, in band class where she played the erhu, Aang tried to play the tsungi horn and got chided by the music teacher for dancing in place while playing. Nevertheless, On Ji was amused by the dance steps and was even asked to be shown some dance moves by Aang.
On Ji was later invited to Aang's dance party. To get people to start dancing, Aang picked On Ji out of the crowd. She blushed, shyly took his hand, and started dancing with him. After this, the rest of the group started dancing around to the music. Later, Aang and Katara began dancing together, and On Ji and the rest of the class began watching in awe as they performed many advanced moves. However, the party was soon broken up, as the headmaster, having been informed by Hide about the party, came into the cave searching for Aang. On Ji, along with the other students, put on a headband to confuse the pursuers in order to help Aang and Team Avatar escape.
On Ji was kind and plucky with a sweet and easygoing personality, as well as a sense of humor. She was friendly and welcoming to others, most notably Aang when he enrolled in the Fire Nation school. She displayed a trustworthy attitude, as she promised Aang to not reveal Momo's presence after she discovered them together and kept her word. Even when the principal was searching for Aang, On Ji helped to protect him.
Avatar: The Last Airbender
Book Three: Fire (火)
- 302. "The Headband"
- On Ji's hairstyle resembles that of Chihiro/Sen's from Hayao Miyazaki's Spirited Away, which has been cited by the creators as one of their inspirations.
- On Ji was named after Angie, a member of the staff.
- On Ji was one of the few Fire Nation natives who did not have the standard black hair and amber eyes.
- O'Bryan, John (writer) & Dos Santos, Joaquim (director). (September 28, 2007). "The Headband". Avatar: The Last Airbender. Season 3. Episode 2. Nickelodeon.
- From older Avatar: The Last Airbender official site, originally on Nick.com. Encyclopedia now broken, archived at The Lost Lore of Avatar Aang - Character: Onji.
- Avatar Extras for "The Headband" on Nicktoons Network.