The Uchiha Clan is widely known as the clan with an incredible dojutsu called the Sharingan, or the Copy Wheel Eyes. They are also known as adept genjutsu practioneers and their firestyle. The clan belongs to Konohagakure no Sato and hails from Hi no Kuni.
Fire doesn’t discriminate. It merely burns. Such is the way the fire works.
The Uchiha take fire (and fanning the flames) very seriously. They embody it, they take it into themselves even when others say they should not. Even why they know it is a bad idea. Such is the Uchiha way.
The Uchiha are a people of intense passion and deep conviction. They believe in what they believe, hellfire or highwater. When they love, it is a love that could rival the sun in pure luminescence. When they hate, it is an all consuming wildfire, destroying any pretense of thought or reason. All that remains is the emotion, the fire.
Adding to this, the Uchiha are a proud people. They love themselves for who they are (except when they hate themselves with equal fervor). They are proud to be Uchiha, they are proud to carry the name. They are devoted and fanatical. Some even refuse to wear armor, soas to not cover the clan’s symbol they wear upon their backs.
While it may sound like as a culture, the Uchiha are two-faced, such is not the case. The Uchiha are remarkably consistent. The fire burns just as readily as it always does. This stereotype comes more from how easily the Uchiha switch from love to hate. Sometimes all it takes is something small, and it catches ablaze, becoming hot with rage and hate. This is often called the Uchiha’s Curse of Hatred. It is so easy to destroy, so easy to hate, that many often forget that fire is a warming and vital thing as much as it is a consumer.
The Uchiha claim their descendance from the same bloodline as the Senju, but of a different relative. Where the Senju claim they sprang from Hagoromo, the Uchiha claim ancestry with his brother, the fiery and pugnacious Indra.
The two clans have been fighting since the dawn of time, even if such fighting doesn’t amount to anything anymore. There is a fundamental divide in the way do things, even if they now work together under the same banner and same nation.
Where the Senju thrived on structure and their Elemental Release, the Uchiha made their name in quickly adapting tactics to suit the situation, copying their enemy’s abilities and methods, and then running them over with a combination of assassination and good old fashioned brute force. In a way, they would have the perfect combination.
The two clans fought for decades (some would argue millennia) in prehistory before coming to a stalemate. For the first time in forever, the two clans decided to mutually set apart their animosity for one another and found a village together: Konohagakure no Sato, the Village Hidden in Leaves.
The Uchiha have fought in all of the major world wars, rallying behind their clan, the Will of Fire, and their own pride as Shinobi. In recent memory, only one Uchiha has been Hokage: The Sandaime Hokage, one Uchiha Eiji.
The Uchiha consider the Sandaime Incident to be one of their greatest qualms with the Senju. It was through their miscommunication and insolence that their Kage and Clan Leader was slain. The Uchiha were at odds with one another of what to do.
The Senju leader, called for a mass cleansing, a time of blood and burning, to find the man’s murderer. The Senju found themselves rid of the pollution that turned the Uchiha against them, but relations have never been the same since. The Uchiha turn from love to hate so easily, and they do not forgive without a fight.
In modern times, the Uchiha have gone through a period of intense growth and rather steep dieback, keeping their numbers relatively even, if not exceptionally stable. However, there is no chance of them leaving Konohagakure, the village they helped to found, any time soon.
The Uchiha are not ones for formal hierarchies. At the most, they have a meritocracy. Those with the most power, the most charisma, and the most legitimate claim to the leader position are the ones that gain sway with the clan.
Disputes are settled either with open fire, arguments and fistfights in the street- or incredibly secretively, anger simmering down into hatred, poisoning and backroom politics and other such underhanded methods being commonplace. Woe betide anyone who angers an Uchiha this far.
Perhaps it's because of this volatile nature that the Uchiha have a Clan Leader position at all. There needs to be someone to reign in the clan and keep them from lighting the city on fire as well as center the clan's loyalty and aims. The Clan Leader is the one who makes all public decisions for the clan, as well as lead them in times of war. As mentioned, they are expected to be the strongest and the most able to lead. Whether this strength is in fire and weaponry, or charisma and backroom politics varies from Leader to Leader.
The famed Copy Wheel Eyes of the Uchiha are a gift only a few can achieve, and even then, they come with a steep cost. Thos with the Sharingan start off with No Tomoe, and through pain and tragedy can gradually awaken new powers within their blood, manifesting as tomoe on their iris.
The Uchiha without Tomoe are the most common among the clan, who have no noticeable abilities of the Sharingan, but have the potential to do so. Many No Tomoe users have discolored or unnatural eye colors, usually of shades of red.
The "Eye of Insight". This is the most basic form of the Sharingan. True to the name, the Eye of Insight gives an Uchiha incredible sensory awareness, allowing them to see chakra itself, though not to the extent of its cousin the Byakugan. Atop of this, One Tomoe gives the user a good sense of an opponent's actions, though not to a supernatural degree. This Tomoe is generally awakened by an Uchiha having a strong emotional reaction to a tragedy in their life (usually the death of someone) though it has been known to awaken during periods of extreme stress protecting another.
The "Eye of Hypnotism", Two Tomoe increases the abilities of the Eye of Insight, as well as allowing the user to produce a new and unreproducible set of hidden Sharingan Genjutsu, of which the Uchiha are notorious for. Some have claimed that an Uchiha can hypnotize anyone just by looking at them, but that is an exaggeration for all except the most skilled Uchiha Illusionists. In terms of actually copying, the second Tomoe allows the user to be able to reactively dodge fast moving projectiles, as well as predict an opponent's moves just by watching minute twitches of their muscles. It is not infallible, but is very powerful. This Tomoe is almost universally awakened by intimate tragedy- the death of a parent of loved one, the destruction of a village, and other such awful things.
Last but not least, the Third and final Tomoe is the highest amount of Tomoe an Uchiha can have at once. This is where the Uchiha get their true fame as copycats. Three Tomoe allows an Uchiha to truly copy any jutsu they see performed, even if it does not grant them the capabilites to actually perform said jutsu. Someone with no legs is not going to be kicking people, Sharingan or no Sharigan. The legends of Uchiha being able to stare down Bijuu come from the prowess of the Third Tomoe and the Mangekyo. It is a terrible and deadly power to behold. There is no set requirement for the Third Tomoe, provided the event is tragic or infuritating enough to deeply shake the Uchiha to their core. This tends to overlap with the requirements to obtain the Second Tomoe.
The "Kaleidoscope Eyes" a special transformation only achieveable when the user has already been inflicted with Three Tomoe, the Mangekyo allows a user to warp reality with their sheer force of will, and each pattern and abilities their eyes produce varies from person to person. The legends state that the Mangekyo can only be awakened when one watches a sibling or lover die and cannot or will not do anything to stop it, forever changing the shinobi. Many Uchiha have historically misunderstood this criteria as the user needing to be responsible for the person's death, and for that reason they developed the practice of killing their closest friends in order to gain the Mangekyō Sharingan. Be warned, overuse of the Mangekyo has long been known to reduce the vision of it, eventually robbing the shinobi of sight entirely. That is, unless they can find a new pair of eyes...