Shisui Uchiha

うちは シスイ, Shunshin no Shisui

Shisui Uchiha (うちはシスイ, Uchiha Shisui) was feared as "Shisui of the Body Flicker" (瞬身のシスイ, Shunshin no Shisui) and was one of the most talented of the Uchiha clan. Shisui was the best friend of Itachi Uchiha; in fact, Itachi thought of him as an older brother. He was found drowned in a river from what appeared to be suicide, though the Konoha Military Police believed it to be murder. It was later revealed that Shisui had been ordered to keep tabs on Itachi. Itachi later admitted to Sasuke Uchiha that he had murdered Shisui to obtain the Mangekyō Sharingan, forging Shisui's handwriting on his suicide note with the help of the Sharingan. (Source: Narutopedia)