BACK STORY OF UCHIHA CLAN

The Uchiha are descendants of Indra Otsutsuki, the elder son of Hagoromo Otsutsuki. Through Indra, the Uchiha inherited Hagoromo's"eyes", granting them powerful spiritual energy and chakra. As part of the so called "Curse of Hatred" first displayed by Indra, Uchiha are sunject to powerful emotions, these emotions typically starts as love for a friend or family member that then become overpowering hatred when the object of their love is lost. This lost, whether actually experienced or merely threaten, awakens an Uchiha's Sharingan.