Izuna Uchiha

was the younger brother of Madara Uchiha, who was known as the strongest Uchiha. He bears a striking resemblance to Sasuke 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, 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 honorably in battle, fighting to the death even in a blind state.

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. It's hinted like Madara, he killed someone close to him to obtain the Mangekyō Sharingan. This means he had a ruthless and ambitious side to him.

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 high levels of chakra, even for Uchiha members.

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 led to his eventual death on the battlefield.

madara loved his brother

Trivia

 * is the name of a wind spirit, and can be translated as "rice-rope."
 * He and Obito Uchiha have some similarities:
 * 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.