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Eighty years prior to the start of the series, Izuna and his older brother were said to be equals as the most gifted members of the Uchiha clan, and they usually competed with each other everyday in order to get stronger. Both awakened their Sharingan early in life, and they became the first Uchiha to awaken the Mangekyo Sharingan. Madara used the power of his Mangekyo Sharingan to take control of the clan, with Izuna at his side. When Madara eventually went blind, he took Izuna's eyes to regain his sight. Itachi Uchiha suggested that his eyes had been taken by force, but Madara insisted that Izuna had willingly given up his eyes for the good of his brother and the clan. According to the Third Databook, Izuna later died in battle.
As the younger brother of Madara Uchiha, who was the strongest of the clan, Izuna himself was said to have been equal to his brother in every way. Both of them had exceptionally high levels of chakra, even for Uchiha members.
Izuna's Mangekyo Sharingan, developed sometime after Madara's, took the appearance of three bars stretching out of his pupil. When Madara took his eyes, the two's Mangekyo combined. Izuna's loss of his eyes rendered him blind, but he managed to survive, and continued to battle. However, with this sudden disability, it led to his eventual death on the battlefield.
- Izuna (飯綱) is the name of a wind spirit, and can be translated as "rice-rope."
- Izuna shared a birthday and blood type with fellow Uchiha, Obito.
- Izuna's hobby was to train with Madara.