Izuna Uchiha

was the younger brother of Madara Uchiha, who was known as the strongest of the Uchiha.

Background
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 Mangekyō Sharingan. Madara used the power of his Mangekyō 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; however, Madara insisted that Izuna had willingly given up his eyes for the good of his brother and the whole clan, seeing that Madara needs to remain strong to protect the clan from its increasing enemies then. According to the Third Databook, Izuna later died honorably in battle, fighting to the death even in his blind state.

Appearance
Izuna has long dark hair that is tied in a ponytail that reaches his lower back. He wore what most Uchiha wear, a blue shirt with the Uchiha Crest on his upper back and blue pants that are wrapped up in bandages at the ends. On his waist, he had a bandage belt that held a sack that presumably holds ninja tools. He bears a striking resemblance to Sasuke Uchiha.

Personality
Izuna Uchiha was a harmonic and devoted person according to the third Naruto Databook. He appeared to be competitive with his brother Madara in terms of skill.

Abilities
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 strong chakra, even for Uchiha members.

Izuna mastered his Sharingan at a very young age, alongside Madara. Izuna's Mangekyō 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 Mangekyō 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 eventually led to his death on the battlefield.

Trivia

 * is the name of a fox spirit in Japan and of a mountain. The latter is usually called Mount Iizuna, though. Iizuna, written with the same kanji, is also the Japanese name for the least weasel.
 * He and Obito Uchiha have some similarities:
 * They both died in battle.
 * They both gave their Sharingan to another person.
 * They both have the same birthday and blood type.
 * According to the Third databook:
 * Izuna's hobby was to train with Madara.
 * Izuna was devoted and harmonic.
 * Izuna died in battle sometime after Madara took his eyes.