Hirokazu was only 4 when Root had taken him away from his brother, Karite. He would shout and scream for help as he awakened his Sharingan that night, unknowingly of course. The Root agents took the young Uchiha to their hideout and subjected him to horrible genjutsu to make his sharingan mature faster...as Danzo wanted him to awaken the Mangekyou at a very small age as to make him fluent in it's use later on when he would get the Eternal Mangekyou...but that was all later on. It had been about seven years since that night, and Hirokazu now possessed all the traits of a foundation member