Kagami Uchiha

was a shinobi from Konohagakure's Uchiha clan who along with his team-mates Torifu Akimichi and Danzō Shimura were direct subordinates of the Second Hokage, Tobirama Senju.

Background
During the First Shinobi World War, he and his team-mates Danzō, and Torifu went on a mission with Team Tobirama. Pursued and ultimately surrounded by Kumogakure's Kinkaku Squad, the group discussed their options, where Kagami noted that Koharu's plan of an ambush wouldn't work and that instead a diversion was needed to lure the enemy away. He then listened as the Second, who had nominated himself as the decoy, appoint Hiruzen as the Third Hokage. Not much is known about Kagami's life after this. A close friend of Danzō Shimura, he saved the latter many times, becoming one of few people Danzō truly trusted.

He later died at some point before the Uchiha clan massacre.

Personality
Along with a strong devotion towards his own clan, Kagami was noted to be greatly dedicated to the protection of Konohagakure, having accomplished much for the sake of the village. His sense of loyalty was so great, he never fell victim to his clan's Curse of Hatred, something that normally had a high probability of happening after awakening the Sharingan. For this reason, he was one of the few Uchiha that Tobirama believed in as well as one of the six people Tobirama chose to work directly under him.

Appearance
Kagami had short, black, unkempt hair which fell over and around his forehead protector, framing his face. The anime actually depicts Kagami's hair a bit more kept. During the First Shinobi World War, he wore the standard Konoha outfit of the time which consisted of a black suit with grey armour covering the chest, thighs, and shoulders, arm guards, a forehead protector, a kunai holster on his right upper leg, sandals, and a pouch strapped to his lower back with bandages. At other times, his attire was that typical to the Uchiha clan and included a high-collared, dark-coloured shirt.

Abilities
As an Uchiha, Kagami had very strong chakra. He was also one of the members that were able to awaken his clan's kekkei genkai: the Sharingan, which granted him various advantageous abilities. These included seeing the flow of chakra, the ability to easily recognise genjutsu and different forms of chakra, some predictive capabilities, as well as the ability to copy techniques that the user sees amongst other things. In the anime, his visual prowess was praised by Danzō to be crucial in saving his life many times. Shisui, Kagami's descendant and one of the most powerful Sharingan users of the Uchiha himself, openly admitted his inferiority to his ancestor as a shinobi.

Trivia

 * Kagami means which are heavily associated with Uchiha. For example,  in Mangekyō Sharingan literally means mirror of ten thousand flowers and one of the sacred weapons of Itachi Uchiha's Susanoo is the Yata Mirror.
 * While it was said that Shisui Uchiha is Kagami's, their exact relationship is unknown.