there is the initial mystery of the spirits, both snakes and the girl with the hat, shady, immortal, omniscient of the protagonist's needs and people around him (although this is just for the humor), of the knowledge that Katara in book 3, she hides information from the MC, but she knows about the mission, which on screen was never revealed to her, and old Toph, Azula and Mai who seem to understand too, all this makes me think there was a story that the protagonist hasn't experienced yet. in their timeline but that they (Katara, Mai, Azula, Toph) have already experienced.