The Sharingan – Copy Wheel Eye – is the doujutsu of the Uchiha Clan. It originated with Otsutsuki Indra, the progenitor of the clan and elder son of the Sage of Six Paths, and its powers are derived from the Rabbit Goddess’ Rinne Sharingan that she acquired from consuming the fruit of the God Tree. It is known as one of the Three Great Doujutsu alongside the Byakugan and the Rinnegan.

It has six abilities which can be broadly classified into two categories called the Eye of Insight and the Eye of Hypnosis. The abilities of the Eye of Insight relate to the physical perception of the world around oneself, while the abilities of the Eye of Hypnosis relate to the spiritual ability to perceive and utilize chakra. The powers of the Eye of Insight are always active as long as the Sharingan itself is active, however, the powers of the Eye of Hypnosis must be consciously accessed by focusing additional chakra to the eyes.

Awakening the Sharingan

Otsutsuki Indra possessed the Sharingan from the day he was born but his descendants needed to awaken the doujutsu for themselves.

To do so, one must experience a powerful emotional triggers in regards to a person precious to them – this emotion can be positive, driven by a desire to protect or reunite with a loved one, but per the clan’s primary occupation as shinobi, it is more often negative, brought on by great pain, shame or loss.

When this powerful emotion is first experienced the brain releases a special form of chakra that affects the optic nerves, transforming the eyes into Sharingan; for that reason the Sharingan is described as the eyes that reflect the heart. Unlike the Byakagun, only a relatively small number of Uchiha ever awaken their bloodline.

The Sharingan has three stages of development, each of which is demonstrated with the appearance another tomoe as it unlocks new powers.

When first awakened each Sharingan usually has only one tomoe. Most of those who awaken it are young children driven to extreme emotions by their warring lifestyle before they have matured. Late bloomers might awaken the Sharingan with two tomoe in one or each of their eyes instead. Otherwise, through training and continued use, the Sharingan will develop a second tomoe and then, upon full maturation, a third.

First Tomoe

The first level of the Eye of Insight is the clarity of perception. The doujutsu is able to perceive far more visual information than a normal eye and processes it for the user. They see everything in perfect detail, from the smallest twitch of a person’s muscles to individual grains of sand on a beach. The user can see much farther than normal, as well as see much smaller objects in greater detail than normally possible, and it can quickly adjust to extreme changes of light without harm or see within low-light conditions.

The way that the Sharingan gleams in the dark as it reflects any available light has even been used by the Uchiha in psychological warfare.

Their enhanced processing power means that they are also able to perceive and follow extremely fast moving objects that would appear as just a blur to a normal person. This allows them to keep up with a faster or tricky opponent, if not tactivally maneuver them into a disadvantageous position. It also aids them in seeing their opponent’s hand-seals when casting jutsu which can help them discern the mechanics of them depending on which hand-seals are used, or avoiding counter attacks that couldn’t have been seen with ordinary eyes.

But the greater the difference in speed between the user and the enemy then the less effective this ability becomes. Even if the Sharingan can perceive their movements, if their own body isn’t fast enough to react to what they can see then they can still be overcome.

Another benefit of this enhanced clarity is the ability to recognize most non-Sharingan based visual genjutsu. Because the user can see the world in far greater detail and with far greater focus, they will easily detect even the smallest irregularity or flaw in the illusion which a normal person, including the creator of the genjutsu, would overlook. Only someone who has the Sharingan themselves can possibly craft a visual illusion with high enough fidelity to fool another Sharingan user for long.

The first level of the Eye of Hypnosis is the perception of chakra. The user is able to see chakra on a visible spectrum as different colors, unlike ordinary people who can only see it in high quantities or when transformed by jutsu. This allows them to see through most clone jutsu and detect those using chakra to hide or disguise themselves. This perception even penetrates through solid objects for some distance, allowing the user to discover chakra-charged people and objects (such as chakra-molding ninja or ninjutsu-based landmines) hidden underground, in trees or behind walls.

This ability also gives the user an incredible defense against any normal kind of genjutsu, including those that aren’t visual based, because they can see the chakra of a targeted genjutsu as it travels to and enters their own body as well as the “anchor” of any area-based genjutsu. This foreknowledge ensures that a ninja actively focusing chakra to their Sharingan can almost never be surprised by an illusion, giving them time to fortify their chakra system to resist the incoming genjutsu and to better prepare a counter for it once they are ensnared.

Second Tomoe

The second level of the Eye of Insight is mimicry. The user is now able to instantly memorize any physical movement they witness and replicate it if it is compatible with their body structure. This allows the user to easily read another person’s lips, or copy another person’s writing just by watching and mimicking the movements of their pencil. Any kind of physical skill can be quickly learned in this way, from playing an instrument to operating complicated machinery.

This memorization applies to any type of taijutsu they witness as well. As long as their movements are within normal human limitations, the Sharingan user should be replicate mimic them exactly with their own body. However how well this is imitatation works depends on the individual’s strength, speed, stamina, reflexes, flexibility and other physical factors. If they mimic a skill that is beyond them, they can cause strain of their body that could possibly result in permanent injury if they can successfully perform it at all.

One does not even need to see the full extent of an individual’s fighting style to successfully mimic it with the Sharingan. By visualizing their movements based on the information they had memorized before, they can essentially mimic the result of that image training to acquire the same capabilities and movements with enough effort.

The second level of the Eye of Hypnosis is perception of chakra flow. The user can now not only perceive chakra, but also the way it flows throughout the human body. This allows the user to detect irregularities in the chakra flow of others, such as being under the influence of a genjutsu. This also greatly aids in the learning and mastery of genjutsu, as the user is able to directly see exactly how their genjutsu affects the flow of chakra in the brain of another person.

Being able to see their chakra flow also allows them to assess chakra levels so they can detect when an opponent has exhausted their stamina, essentially meaning that they are defenceless. On the other hand, it can help them predict when they are preparing to cast a jutsu based on the chakra building up inside them.

Third Tomoe

The final level of the Eye of Insight is prediction. The Sharingan can now use its ability to read and copy the body language of other people to predict their movements, giving the user an incredible advantage in combat. To the user, this ability is experienced within the mind’s eye as a “shadow” of the other person moving a short distance ahead of their real body. By avoiding the points that the shadow is aiming for and positioning themselves to take advantage, they anticipate and avoid the enemy’s attack while launching their own to turn the tables.

To other people, it can seem like a form of precognition or mind reading and the Uchiha clan had long encouraged this misunderstanding of their bloodline as a form of propaganda.

While powerful, this prediction is not perfect; if the opponent is able to move their body in ways that are unnatural, to suppress the normal tells of their body language and move in ways that are highly erratic and seemingly random, then this prediction can be thwarted as the user struggles to react.

This prediction is also less effective the faster the opponent is able to move. While it helps neutralize the advantage a faster opponent would have, the less time the Sharingan has to calculate their movements then the shorter and less accurate its predictions will be. The prediction will similarly be reduced if the opponent hides or otherwise obscures their body language, such as by wearing a mask and thick, loose clothing.

The final level of the Eye of Hypnosis is projecting chakra. The Sharingan is now able to instantly sends chakra directly from the user into the target’s brain through their optic nerve upon making eye contact. It allows them to manipulate the victim with a unique ability known as Genjutsu: Sharingan by hynoptising them with any genjutsu they have learned without using hand-seals or providing any other tell to alert them of its effect.

As the genjutsu travels extremely quickly, bypassing most of the body’s normal defenses and usually hits the target completely unexpectedly, the effects can be devastatingly effective to a normal person. Because it can be used to cast practically any genjutsu, it is incredibly versatile and serves many purposes: inducing instantaneous unconsciousness in the target; paralyzing the target’s body; forceful extraction of any information the target possesses; relaying of memories to the target; removing genjutsu placed on the target by others; even controlling the target’s actions which may even reflect the Sharingan in the victim’s eyes.

It is a powerful skill even against another Sharingan user who would be able to resist most other genjutsu and such battles consist of genjutsu exchanges as they manipulate one another’s illusions with their own.

Copying with the Sharingan

When the Eye of Insight and Eye of Hypnosis are used together properly upon acquiring the second tomoe, these two powers can be used to effectively copy and learn any ninjutsu or genjutsu the user is able to clearly witness being performed. By memorizing another’s handseals and watching the flow of chakra throughout their body, the user can gain an incredible understanding of the mechanics of their jutsu. If the user also meets all the requirements of the jutsu (chakra control is up to par, body is strong enough, nature transformation is already known, etc) they may even be able to immediately perform the jutsu themselves.

While in theory the user can learn any jutsu this way, in practice it depends on the respective abilities of the copyist and the copied. The more skilled the ninja then the more capable they are of performing advanced, complicated jutsu without needing to use the entire sequence of hand-seals or even most of the hand-seals as they internally perform the necessary shape and nature transformation.

Copying such jutsu is significantly more difficult, as the user must replicate it from observing the individual’s chakra flow alone without knowing which hand-seals had been excluded as unnecessary. So unless they are so skilled that they can mimic the target based on that alone, they would need to practice the jutsu until they achieve the same level of mastery or possess enough knowledge to decipher which hand-seals are needed. Using the Sharingan to copy a complicated A-rank jutsu performed entirely without seals, such as the Rasengan, would be almost as difficult as attempting to learn it the normal way.

Even if they are physically incapable of performing the jutsu themselves, the knowledge is still permanently imprinted in their minds. This includes jutsu that can only be cast with a kekkei genkai which are impossible for anyone to mimic without having the same genetic abilities. If a Sharingan user copied one of these and then acquired the necessary kekkei genkai, they could potentially mimic it themselves.

Transplanting the Sharingan

When the Sharingan is extracted from its original bearer, dead or alive, it will automatically be fixed in its activated state and can be implanted in another person to allow them to use its abilities.

It has been known for Uchiha who have lost one or both eyes in battle from injuries or kinjutsu to have them replaced with the eyes of a recently deceased Uchiha or from a stock of preserved Sharingan kept safe for that purpose. While there are minor differences in using these in comparison to their original eyes, they are generally neglible so one pair can be used as well as another and they can be switched on and off at will.

The Sharingan can be also be transplanted into non-Uchiha. But because they are not genetically compatible with the doujutsu, the eye is forced to consume a large than average amount of the bearer’s chakra to compensate for its insufficient quality. Typically, a non-Uchiha with just a single Sharingan will experience fatigue far faster than a Uchiha with both Sharingan active.

Moreover, it is impossible for them to deactivate the doujutsu so it is always consuming a portion of chakra whereas a Uchiha can just switch it off to conserve their own. Because of this, non-Uchiha would need to cover their Sharingan when they aren’t using it in order to decrease the amount of visual information it needs to process and therefore reduce its chakra usage as much as possible.

In the exceptional circumstance that two people share half of a pair of Sharingan, it is possible for them to see what the other eye is seeing when in relatively close proximity and experiencing extreme emotions. However such an event has only occured once in the history of the Uchiha, long after the majority had died out in fact.

Co-written with Altered Nova