Sharingan (англ. Sharingan, lit. "Copying Eye") is a dōjutsu of the Uchiha clan, manifesting selectively among its members and revered as one of the Three Great Dōjutsu alongside the Byakugan and Rinnegan. Its awakening is triggered by a strong emotional experience directed at a loved one — the brain releases a special chakra that affects the optic nerves and transforms the eyes into the Sharingan, which is why it is called "the eye that reflects the heart." Initially the eye bears one tomoe, but as the bearer's emotional growth progresses, it reaches three, achieving full maturity; all abilities are available from the first stage, merely strengthening with development.
The Sharingan is endowed with two fundamental properties. The "Eye of Insight" allows one to see chakra, distinguishing its colors, sources, and composition, recognize illusions and clones, notice anomalies in the chakra flow of others, and also view chakra through certain obstacles. Perception sharpens to the point of lip-reading, tracking fast-moving objects, and predicting an opponent's actions from the slightest muscle movement. This allows one to read hand seals and copy virtually any technique seen — be it ninjutsu, genjutsu, or taijutsu — reproducing them or adapting them to oneself. The "Eye of Hypnosis" through eye contact instills thoughts and actions into the target, forcing them to divulge information or act in a certain way, often without the victim's awareness. Under full control, the body is directly subjugated, and the pattern of the Sharingan appears in the victim's eye. With this power, the Uchiha became renowned for their ability to suppress tailed beasts, penetrating the subconscious of the jinchūriki and controlling the beast's chakra. The skillful combination of copying movements and suggestion creates the illusion of foreseeing the future.
Additionally, the Sharingan grants access to two forbidden techniques: Izanagi briefly erases the boundary between reality and illusion, turning death into a delusion and rewriting reality, while Izanami traps the target in an infinite loop independent of the five senses, serving as punishment for those who abuse Izanagi. The cost for each of them is irreversible blindness of the eye used.
The Sharingan can be transplanted to someone who is not an Uchiha, but such a bearer cannot deactivate the eye and spends noticeably more chakra to maintain it, which is why they usually cover it with something. Further evolution leads to the Mangekyō Sharingan through the trauma of losing a loved one, and the mixing of Asura's and Indra's chakra can transform the Sharingan into the Rinnegan.
