Oyaji was the leader of a village on Kyoshi Island. When Aang and his friends first arrived on the island, he was initially distrustful of them, believing them to be Fire Nation spies and wishing for Kyoshi Island to maintain its neutrality in the Hundred Year War. However, he later stood beside them, and helped get his people to safety when the Fire Nation attacked.
Oyaji was appointed to the position of village leader around 79 ASC, twenty years before Team Avatar's arrival.
When Avatar Aang, Katara, and Sokka came to Kyoshi Island, Oyaji, Suki, and the other Kyoshi Warriors were initially suspicious of Aang, but they believed that he was the Avatar once he displayed airbending abilities. He was later seen running to Sokka and the other Kyoshi Warriors, appealing to them for help as PrinceZuko and his troops were approaching. He later quietly thanked Aang after the latter used the unagi to extinguish the fires, a result of the fight between Aang and the Kyoshi Warriors and the Fire Nation.
A few months later, he helped Katara and Sokka in their quest to clear Aang's name. He explained the legend surrounding AvatarKyoshi's weapons and clothing while sternly trying to keep the siblings from touching them, and explained the meaning of the picture "Birth of Kyoshi". He also informed Sokka about Suki's departure from Kyoshi Island and the influence the group had on her.