How did Izuna Uchiha -younger brother of Madara Uchiha die? Was he killed by Tobirama Senju or by Madara himself when he seized his eyes?
During a battle with Tobirama, Izuna was mortally wounded by Tobirama's technique.
With Madara quickly rushing to Izuna's aid, Hashirama pleaded with Madara to come to peaceful terms. Seeing his brother begin to consider this offer, Izuna told his brother not to listen to their lies, ultimately making Madara retreat with Izuna.
Madara later revealed that Izuna died from the injury. At the last moments of his life, the dying Izuna had given Madara his eyes so his brother could obtain the Eternal Mangekyō Sharingan to protect their clan.
Because of the blindness caused by overuse of a Mangekyō Sharingan, many people came to believe that Madara took Izuna's eyes by force to regain his sight.