Kotora Uchiha

Like many Uchiha growing up during the Warring States period, much of Kotora's early life was marked by death and tragedy. There was not much of a childhood to be had during this time, and Kotora was forced to grow up quickly in order to survive. It was mainly through his older brother Kouga's machinations that Kotora was whipped into shape, impressed upon him early what he must be capable of to not only live, but to kill others. It was a harsh reality that for a long time Kotora struggled with, and his first kill on the battlefield was what awoke his Sharingan.

As he grew older, Kotora was more capable of steeling his nerves, of killing without remorse, and in time he grew into a formidable Uchiha shinobi, tearing up battle with heat-heavy katon and leaving behind nothing but ash. He honed his abilities to a fine point, but as skilled as Tora grew ultimately he was still not able to prevent the deaths of his brother, his father, and his mother. The more that was taken from him, the less he was able to feel like the war had meaning, like fighting had any fulfillment at all to him. He was loyal to his clan, but his pride in his ability to kill was no longer there.

The end of the war came as a great relief to him and he found it easier than others to assimilate into Konoha upon it's founding- the sting of the loss of his family at the hands of the Senju had long since eroded into a hope for a future that he believed honored his family far more than any bloody victory would. And, well, he could admit some of the loneliness he had begun to feel, a hole in his heart that he found filled by the burgeoning village.
Due to his abilities and his honest loyalty to the village, Kotora was recommended for a position in Konoha's early special-operatives group, what would later formally become the ANBU. Under Hashirama Senju's authority as the First Hokage, his first proper assignment was to aid Tobirama Senju as his personal guard, a choice made by Hashirama to help foster more trust between the clans. Kotora took this assignment to heart, but Tobirama was...less than receptive to it's concept, both out of a lock of trust towards Tora and a lack of belief in the idea he needed a shadow. Much of their early interactions were spent with Tobirama avoiding Kotora, and Kotora playing a sick little game of hide and seek trying to find the man.

Their contention with each other culminated when Tobirama slipped away to go on a mission without waiting, and Kotora found him slumped against a tree, mortally wounded. Though told to report back to Konoha and leave him there, Kotora refused the order and admitted to Tobirama he hoped that in the future Tobirama would would be able to trust him more, not just as a guard but as a friend, before using Hansha to take his wounds upon himself, saving his life.
Luckily, after that their relationship improved, and between doing his actual job Kotora spent significant time assisting Tobirama with his jutsu creation, perfectly content to play guinea pig to the man's curiosities. He learned and became well-practiced in the Shadow Clone Jutsu from him, and helped keep the records of the creation of multiple jutsus.

Over time, something unspokenly intimate grew between them, something neither of them verbally defined to each other or anyone around them. In a better world, Kotora liked to think he would've happily taken the Senju name.

Unfortunately, the peace that created Konoha didn't last, and during the First Shinobi World War Kotora lost his life on a mission across the Land of Water. Despite ANBU regulations, his body was recovered and returned home, and the study of it contributed to the creation of the Edo Tensei.