Due did not appear to be particularly intelligent, usually letting Tho think for him, but he did seem to deeply value family ties and relationships, since he considered himself and Katara to be "kin" as they were both waterbenders. He even called his catgator, Slim, a member of the family. In general, he was dim-witted but very friendly and worked hard alongside his friends and family to keep them happy and well-fed. He also proved to be a master waterbender, and was able to counter an attack from Aang and Katara combined.
While separated from Aang, Katara, and Sokka, Appa and Momo encountered Due and Tho, who began hunting them down. Aang eventually found Appa and Momo and stopped Tho and Due, who were more than happy to find fellow waterbenders outside of the swamp in Aang and Katara. Due, Tho, and Huu then invited the team to their camp to share a meal.
Months later, Due, together with his fellow tribesmen Tho and Huu, helped with the initial land stage of the invasion, but remained behind when the invasion force started scaling the volcano. When the eclipse ended, the Fire Nation deployed its airships to the beach to destroy the submarines, the invasion force's only means of escape. The three waterbenders tried to protect the submarine fleet, but their efforts proved to be in vain. Like the rest of the adult fighters, Due was detained in a Fire Nation prison, but was released at the end of the Hundred Year War, and later attended Fire LordZuko's coronation ceremony.