Shisui Uchiha

was a shinobi from Konohagakure's Uchiha clan and was renowned as.

Background
Shisui was noted to be one of the most talented members of the Uchiha clan. At some point in the past, he fought with Ao. Ao retains an acute memory of Shisui's chakra and ability to control others with his Sharingan. Because of this, he recognises that Shisui's right arm and eye were transplanted into Danzō. Danzō himself had taken the eye from Shisui some time before his death.

About six months after joining the ANBU, Itachi began to act oddly, and Shisui was instructed by the Konoha Military Police Force to keep tabs on him. Soon afterwards Shisui was found drowned in the Naka River with a suicide note stating that he was tired of carrying out the clan's duties. The police suspected that Itachi had murdered him and used his Sharingan to fake the suicide note, since Shisui was very devoted to the clan, and suicide would have been highly unusual and uncharacteristic. After this, Danzō took Shisui's right arm and Sharingan and implanted them into himself. Itachi later confessed to Sasuke that he did kill Shisui and forged the suicide note, all in order to awaken his own Mangekyō Sharingan. Shisui's corpse has apparently disappeared, as Kabuto Yakushi cannot locate it.

Personality
Shisui was Itachi's best friend; in fact, Itachi thought of him as an older brother. However, Shisui was also very devoted to the clan, which is why the Konoha Military Police Force asked him to spy on Itachi. It is because of this devotion that the police did not believe he could have committed suicide.

Appearance
Shisui had dark unkempt short hair and a flat nose. His eyes were also presumable dark as customary of most of the members of the clan (although his eyes have not been seen without the Sharingan activated). He also had markings around his eyes that were turned upwards at each end. In the anime however these lines are broken instead of whole. He seemingly also wore the standard attire of the Uchiha clan which includes a high collared dark outfit along with a tantō strapped to the right side of his shoulder.

Abilities
Shisui was noted to be one of the most talented members of his battle-excelling clan. He had earned the nickname of "Shisui of the Body Flicker", possibly implying that he had great mastery of the Body Flicker Technique.

Sharingan
Like many members of his clan, he was also a wielder of the Sharingan. He was praised alongside Itachi as for having the greatest mastery and sheer power in its usage.

Mangekyō Sharingan
In addition, he also possessed the Mangekyō Sharingan. With his Mangekyō Sharingan he could use a unique dōjutsu of the highest calibre. It allowed the user to control the mind of the target to the point where even the one it was being used on wasn't aware of it themselves. This ability was apparently so unique and powerful, that Madara Uchiha himself (despite having access to both the Mangekyō Sharingan and the Rinnegan) coveted it, and was angry that Danzō managed to destroy the eye that was transplanted into him from Shisui at the moment of his death. Another testament to his prowess is that Kabuto Yakushi wanted to revive him for the war but failed to find sufficient DNA samples.

Trivia

 * Shisui's name has two interpretable meanings. Combining the words and, Shisui would mean "death water", which is a reference to his death by drowning.  alone means "still water" or "stagnant water".