Mangekyō Sharingan

The, noted to be the , is an advanced form of the Sharingan that has only been activated by a handful of Uchiha. It was also awakened by Kakashi Hatake — a non-Uchiha.

Overview
The Mangekyō Sharingan has the ability to control the Nine-Tailed Demon Fox, a feat only Madara and Obito Uchiha have displayed thus far. It also grants them access to other powerful techniques. The Mangekyō Sharingan is distinguished from a normal Sharingan by its appearance, which changes the form of the tomoe seal. Unlike the Sharingan, the appearance of the Mangekyō Sharingan differs from user to user with all known wielders of the dōjutsu having eyes that resemble variations of pinwheels.

The Mangekyō Sharingan is awakened through the trauma experienced from the death of a person very close to the Sharingan user. With the user normally having to witness or experience this first hand, Uchiha throughout history have killed a person very close to them in order to expedite this process,though how Shisui gained his Mangekyō Sharingan has yet to be revealed. To obtain the Mangekyō Sharingan, one must feel the emotion of losing a friend or family, as merely killing them or watching them die will not activate it.

Over time, use of the Mangekyō Sharingan's techniques deteriorates the user's eyesight to the point of blindness. Only by taking and transplanting the Mangekyō of another Uchiha — integrating the two pairs of eyes in the process — can the vision be restored, a process that results in the creation of an. It would appear that the tighter the blood ties are between the "donor" and the "receiver", the better it is for compatibility — a sibling for example seems to make the best donor. The time from fusing the donor's Mangekyō with the receiver's Mangekyō to the point of full recovery is at least several days as seen in Sasuke's case. Not only does this process permanently restore one's eyesight, but it also gives the person even greater increases in power. The Eternal Mangekyō Sharingan also changes form from the original Mangekyō form, to what appears to be a fusion of the wielder's own Mangekyō with the transplanted one. If an Uchiha with the Mangekyō Sharingan is reincarnated through the Summoning: Impure World Reincarnation technique, they gain the ability to use the Mangekyō Sharingan for extended periods of time without complaints of any deteriorating vision, as seen in Itachi's case.

Madara was able to change his Eternal Mangekyō Sharingan into the Rinnegan after implanting the DNA of Hashirama Senju into himself, though the dōjutsu only awakened years after the implant, when Madara's natural lifespan was almost over.

Itachi Uchiha
Itachi Uchiha gained the Mangekyō Sharingan by aiding his best friend, Shisui, in killing himself. With the Mangekyō Sharingan, Itachi was able to use at least three powerful techniques. With his "left Mangekyō" he could use Tsukuyomi, an extremely powerful genjutsu that allowed him to distort the victim's perception of time, torturing their psyche for what seemed like days in a matter of seconds. With his "right Mangekyō" he could use Amaterasu, a ninjutsu which creates virtually-inextinguishable black flames at the user's focal point that continue to burn until the target is reduced to ash. The last of these known techniques was Susanoo, which allowed Itachi to summon a massive ethereal warrior. This entity fights on behalf of Itachi and shields him from most attacks. According to Zetsu, when it is combined with the Yata Mirror and Sword of Totsuka it essentially made Itachi invincible. Itachi's Susanoo has three forms which it goes through: an incomplete skeletal form, a complete warrior-like form and a final form that resembles a yamabushi.

Use of the Mangekyō Sharingan put a great strain on Itachi's body and would quickly deplete his chakra reserves to the point that after using it three times in a day, he deactivated his eyes to their normal state. A clone containing 30% of his chakra couldn't use it once. By the time he battled Sasuke, his sight had been reduced to a large blur, yet having resolved himself to dying at the hands of his brother, pushed past this limitation and used his Mangekyō Sharingan more than three times as well as other techniques. After Itachi's death, Sasuke, at first, refused to take his eyes despite his own deteriorating eye-sight, but eventually did so he could face Naruto at his best, obtaining an Eternal Mangekyō Sharingan in the process.

Kakashi Hatake
Kakashi Hatake's Mangekyō Sharingan awakened, after the trauma of killing Rin Nohara with his own hands. Despite its awakening, Kakashi only began to use the Mangekyō during Part II of the series, whether he knew he possessed it beforehand is unknown. Regardless, with this dōjutsu Kakashi can use a space–time ninjutsu known as Kamui to create a barrier and send a target to the other dimension and afterwards teleport them back in a new location. The barrier requires considerable effort to aim with precision, leaving Kakashi's chakra significantly drained; especially considering that Kakashi is a non-Uchiha. Initially, he could only handle two uses in a single day, left crippled for over a week from a third use, and had poor control at aiming it. However, after much practice, he can now even control the size of it to only affect the target he chooses, and use precise aim to warp speeding targets. He can also use it twice in quick succession, without showing immediate chakra drain and fatigue, to counter Sasuke Uchiha's Susanoo arrows. By the time of the Fourth Shinobi World War, Kakashi became able to use it several more times in a single day, even with multiple other chakra-taxing techniques, and recover from an over-usage much quicker. His skill has grown to the point that he can use this technique on himself.

Obito Uchiha
After witnessing Rin Nohara dying at Kakashi's hands, Obito Uchiha awakened his Mangekyō Sharingan. As the two share the same pair of eyes, Obito's Mangekyō Sharingan also allows him to use Kamui, although his version differs from that of Kakashi's. Whereas Kakashi's version works on targets from a distance, Obito's version requires him to first make physical contact with a target besides himself and afterwards, he can teleport the target back from the other dimension. In addition, Obito's version gives him a form of "intangibility", brought about by him teleporting portions of his body for short periods of time to the other dimension in order to avoid damage or pass through obstacles. This also provides Obito immunity from Kakashi's Kamui being used directly against him since they both access the same dimensional space, though attacks being warped by Kamui to the other dimension can bypass Obito's intangibility. He can also combine the spatial distortion of the Kamui with his Fire Release techniques to create a massive vortex of flames.

Madara Uchiha
Madara Uchiha, along with his younger brother Izuna, were the first Uchiha to awaken the Mangekyō Sharingan. He eventually began to go blind from overusing it, and only by taking his younger brother's eyes, did he regain his sight. This also gave him an Eternal Mangekyō Sharingan which granted him even greater power. His Eternal Mangekyō Sharingan looks like his original one, overlapping that of Izuna's.

Madara became one of the few to awaken Susanoo, as a result of awakening Amaterasu and Tsukuyomi in both eyes. Madara boasts a "perfect" full-bodied Susanoo that is equal in power to that of a tailed beast. He could also use his Susanoo to shape it around Kurama to protect it from Hashirama Senju. His Susanoo has shown unique attributes in that it has two faces and two sets of hands instead of a single face and three hands as seems to be the standard. Madara can also completely control the Nine-Tails with the dōjutsu,  a feat which no one else but Obito Uchiha has achieved.

Izuna Uchiha
Alongside his brother, Izuna Uchiha and Madara were the first two people in the clan to awaken the Mangekyō Sharingan. Madara later took Izuna's eyes to regain his deteriorating vision. There are many, and somewhat conflicting accounts of how Madara acquired the eyes; some note that Izuna willingly gave up his eyes for the Uchiha clan's sake, another implied that Madara took them by force.

Sasuke Uchiha
Sasuke Uchiha awakened his Mangekyō Sharingan after learning the truth about his brother, Itachi; filled with grief from learning that Itachi was not the villain he imagined him to be and the role Sasuke placed in Itachi's death. Unlike other Sharingan, which have red pupils, and black irides, and red sclerae, Sasuke's Mangekyō is the first one that is shown to have a black pupil, red irides, and black sclerae.

Sasuke has been shown using the same Mangekyō Sharingan techniques as Itachi, but in an inverted manner. With his "right Mangekyō" he can use Tsukuyomi to break a target's will and paralyse them. Danzō Shimura stated that Sasuke's version is not yet capable of altering the victim's perception of time, and thus is vastly inferior to Itachi's. With his "left Mangekyō" he can use Amaterasu. It has been implied that his skill with Amaterasu surpasses Itachi's, as he is able to use Blaze Release: Kagutsuchi with his "right Mangekyō" to apply Shape Transformation to the flames, as well as extinguish them at will. Sasuke has displayed the ability to use Susanoo, which he can even partially manifest to fit the situation, such as using a ribcage for defence or manifesting only an arm to interact with his surroundings. Sasuke's Susanoo develops in stages during various battles; he first starts using an incomplete version against the Fourth Raikage, develops a version capable of firing arrows while fighting with Danzō, and later forms a version almost identical to Itachi's during his battle with Kakashi. Sasuke's Susanoo appears more demonic than Itachi's.

Due to his high chakra reserves, Sasuke is able to use the Mangekyō Sharingan techniques more than three times a day. Sasuke can maintain Susanoo for extended periods of time, on top of using the Amaterasu and Tsukuyomi several times a day along with some other chakra-consuming techniques like the Chidori. Like with all other wielders, Sasuke's use of the Mangekyō Sharingan puts a great strain on Sasuke's body and eyes.

Initially, Sasuke refused to transplant Itachi's eyes to restore his vision even when it was reduced to a heavy blur at best, claiming that his views were different from Itachi's. However, after meeting Naruto again and being shocked at his determination to save Sasuke from his darkness, Sasuke decided to take Itachi's eyes so that he could kill Naruto with his full strength. His Eternal Mangekyō Sharingan takes the shape of his old Mangekyō Sharingan, but incorporates a straightened version of Itachi's Mangekyō Sharingan design into its centre. With his new eyes, the final form of his Susanoo takes on a more ghastly shape. However, it has been shown that Sasuke still has access to his Mangekyō Sharingan's original form.

Shisui Uchiha
Shisui Uchiha awakened his Mangekyō Sharingan at some point through unknown means. It granted him the ability to cast powerful genjutsu techniques, the most powerful of his genjutsu arsenal being Kotoamatsukami. This technique allowed him to manipulate an opponent's thoughts completely without them having the slightest idea that they were being controlled. Furthermore, this technique can be used without eye contact or even the need to uncover the eye if concealed. The only drawback of using that technique was the fact that it would render his Mangekyō unusable for quite some time.

A highly coveted ability, Shisui's right eye was stolen by Danzō Shimura while he was still alive. After replacing his own right eye with Shisui's and infusing some of Hashirama Senju's DNA into himself, Danzō was able to drastically reduce the timespan between each usage of this technique. Shisui entrusted his left eye to Itachi Uchiha and told him to protect the village and the clan's name; Itachi implanted it into a crow which he later stored inside Naruto Uzumaki. Shisui then made it appear as though he had crushed his own eyes in order to prevent a feud over them and erased his existence, though it was thought that he was drowned by Itachi in the Naka River. Both eyes are eventually destroyed, with Danzō crushing his before dying, and Itachi incinerating the crow after it came back out of Naruto.

Trivia

 * In the anime, in the fight against A, the internal intersection lines of Sasuke's Mangekyō Sharingan are replaced by a circle.
 * In the anime, when Kakashi used his Mangekyō Sharingan to warp away Sasuke's Susanoo's arrows, the black and red colours became inverted.
 * The manners in which an individual gains the Mangekyō Sharingan are almost parallel to how an Uchiha awakens their regular Sharingan for the first time, since both need intense emotions to awaken them.