Nini was a resident of the Southern Water Tribe and a friend of Kya when she was a little girl. She was mentioned in a legend told by Katara to her friends, though for this reason it is unclear whether Nini was a real person or just a fictional figure.
When Nini was a little girl, her village fell victim to a devastating blizzard that buried her entire house under snow for weeks. Her friend Kya realized a month later that she had not seen Nini since the storm, and went to visit her house with a few other villagers. When they did not find her or her family, the men went out to search. Kya remained in the house where she heard an ominous voice say, "It's so cold and I can't get warm!" She quickly recognized the voice as Nini's and turned to witness her standing by the fireplace trying to get warm. Her skin was blue like she was frozen. Kya rushed out of the house, but by the time help arrived, Nini was no longer there. Rumors persisted in the Southern Water Tribe that her house was haunted. Afterward, many villagers reported seeing smoke rising from the chimney of her house, as if Nini was still trying to warm herself by the fireplace.
- Nini is one of the few Water Tribe characters who does not have an 'uh' sound in her name.