SHARINGAN
The Sharingan (写輪眼?, lit. "Copy Wheel Eye", English manga: "Mirror Wheel Eye") is a genetic eye technique that naturally occurs in members of the Uchiha clan. It is not immediately present from birth, and first activates in a stressful situation in battle; after this occurrence, the user may utilize the Sharingan freely.[47] When first acquired, the Sharingan has only one tomoe, and as its power increases, two additional tomoe will eventually appear. Kakashi Hatake possesses a single, transplanted Sharingan in his left eye that he received from his teammate, Obito Uchiha.[48] Because he is not a member of the Uchiha clan, Kakashi's Sharingan is always active and he expends chakra rapidly when using it, forcing him to cover it up when not in combat and needing extended rest after long battles.[49] Members of the Uchiha clan expend a negligible amount of chakra when using the Sharingan; Akatsuki member Itachi Uchiha keeps his Sharingan activated constantly. Danzo has also been shown to have a Sharingan in his right eye and a multitude in his right arm.
Over the course of its development, the Sharingan will grant the user three unique abilities. It is most famous in the Naruto world for its ability to memorize and replicate any movement it has seen, allowing the user to copy most opponent's jutsu by memorizing the handsigns/muscle movements and allows them to use the jutsu against them and later opponents.[50] The Sharingan's second ability grants the user increased clarity of perception, allowing them to track and predict the movements and actions of fast-moving objects. This also allows the user to easily recognize genjutsu and different forms of chakra.[48] Its final ability is a brand of hypnosis that suggests actions and thoughts to the opponent, acting as an effective way to produce genjutsu or implant memories in another person.[51]

MANGEKYO SHARINGAN

The Mangekyo Sharingan (万華鏡写輪眼, Mangekyō Sharingan?, lit. "Kaleidoscope Copy Wheel Eye") is a heightened form of Sharingan introduced towards the end of Part I. At that time, the Mangekyo Sharingan is explained to be rare among the members of the Uchiha clan, present only in those who have killed their closest friends.[52] In Part II, this is revealed to be false; after Madara Uchiha became the first to awaken his Mangekyo Sharingan, it became common practice for Uchiha clan members to kill their friends to gain their own.[53] It is also revealed that the Mangekyo Sharingan does not need to be gained by killing a friend; instead, it can be activated after the death of anyone the user is close to. Sasuke Uchiha gains his own Mangekyo Sharingan when his brother, Itachi Uchiha dies.[54] Unlike the regular Sharingan, which appears identical from user to user, the Mangekyo Sharingan's tomoe seal differs between individuals. Similarly, each Mangekyo Sharingan grants the user unique abilities.[55] Its abilities were usually derived from the Japanese mythology. Hence, giving the interpretation that they are one of the divine and most powerful ninja techniques ever used. One feature shared by all Mangekyo Sharingan, however, is the ability to control the nine-tailed demon fox. Other known features of the Mangekyo Sharingan are Amaterasu (天照?), the ability to generate a black flame so hot that it can eat other flames when it is focused on the focal point of the eye; Tsukuyomi (月読?), a genjutsu that traps the opponent in a realm controlled by the user; and Susanoo (須佐能乎?), a summoned mystical being made of chakra which is able to protect and attack for the user. These abilities are only present in Sasuke Uchiha, and his brother Itachi Uchiha, who first derived these powers and transferred them to Sasuke at the moment of his death. Another technique, Kamui, awakened in Kakashi's Mangekyo Sharingan, which grants him the unique ability to open small dimension rifts that are capable of sucking in whatever Kakashi looks at with his Mangekyo Sharingan. Once it has been gained, the user suffers from ever-deteriorating eyesight, a process that is aggravated by repeated use and culminates in blindness.[56] One's eyesight can be permanently restored by taking the eyes of someone else who has the Mangekyo Sharingan, a process that fuses their two Mangekyo Sharingan into one "eternal" form with increased power; the only two confirmed users of the "eternal" form are Madara Uchiha and Sasuke Uchiha, but only the eternal Mangekyo form can control the demon fox and give the user the power to phase parts of his body in other dimensions and return them again to avoid most of attacks.