there is little known about Uchiha Izuna, this is from datebook
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Uchiha Izuna
His older brother, leader of the Uchiha losing his eyesight: a literal synonym of "ruin" for the clan. Izuna chose himself to present his own eyes, without hesitation, without a word. An act tantamount to suicide for an Uchiha, as they owe their fame to their doujutsu...
Caption
-The shinobi at the Uchiha founder's side. He sacrifices his light for the sake of his clan.
Picture comment
-His eyes passed over to Madara, it doesn't take long before Izuna loses his life in battle...
Madara: My (little) brother acknowledged it all. Offering his eyes was his own initiative.
Bottom section
Title (right side): Konoha Information Panels Collection (tn: Arbitrary translation. Alternatives are welcome)... Number Twenty-Eight
Main text
The Mangekyou Sharingan, a rarity even throughout the Uchiha's history. The power it hides is frightening, thus so are the side-effects. As the caster keeps on using it, it takes away their eyesight. For those who master this powerful doujutsu, the apprehension of suddenly going blind is unfathomable. There is only one way to avoid the blindness, which is to steal a new Mangekyou Sharingan from a member of the clan... The vile method employed by Madara. The Mangekyou Sharingan; an accursed doujutsu that cannot go without victims.
Caption
The Mangekyou Sharingan, a blood-stained destiny
Picture comments
-Both awakened to Mangekyou Sharingan, the siblings were prodigiously talented.
-Using his (little) brother's eyes, Madara obtained an eternal Mangekyou Sharingan.