A Quirk (個性 Kosei?, lit. "Individuality"), also known as a Meta Ability (異能 Inō?) by the Meta Liberation Army, is a special, superhuman ability that a person can have. Along with being unique to each user, Quirks are compartmentalized into multiple categories. Quirk users are also limited to one ability and are thus unable to achieve any other.
The first person to manifest a Quirk was a newborn baby in the city of Qingqing; their ability was to emanate light from their body. After that incident, many people around the world began to manifest different kinds of special abilities. While the cause of the Quirk phenomenon is unknown, it has been theorized that the development of Quirks was caused by the spread of a virus carried by mice. Currently, around 80% of the world population possesses a Quirk.
The dawn of this extraordinary era was marred by a breakdown of society caused by the sudden onslaught of criminals empowered by their newfound "superpowers". These superpowers were first referred to as meta abilities before later being called Quirks. In this time, All For One became a symbol of unity in society. He used his Quirk to remove Quirks from those who did not want them and give Quirks to those that did, under the guise of returning society to its prior state of humanity. In this way, he gathered followers who were loyal to him, allowing him to act out his ulterior motives.
As chaos and unrest ensued due to the outbreak of Quirks, ordinary civilians with their own Quirks decided to take matters into their own hands to bring order to society and thus the first "heroes" appeared in the form of Vigilantes and thus beginning the Vigilantes Era.
As society adapted to the new status quo, the Police Force moved to prioritize leadership and to maintain the status quo, and as such, decided not to use Quirks as weapons. To fill that void, the profession of crime-fighting Quirk users, Pro Heroes, began to exist which caused the Vigilantes to slowly disappear. Authorizing the use of powers that could so easily kill, however, was a greatly criticized decision at first.
Over time, it came to garner public support due to the fact that the first people to work professionally as heroes acted morally and upheld the law. However, some members of society were not happy with the the governments' regulations on Quirk usage as they believed that the use of their superhuman abilities should be a right.
A group of Quirk users known as the Meta Liberation Army, led by Destro, had tried to stop the passing of regulations that would restrict Quirk usage. They rebelled against several governments for years before ultimately suffering defeat.
Quirks are inherited genetically through what appears to be Mendelian inheritance and typically manifest in children by the age of four at the latest. Children will either manifest one of their parent's Quirks or a new composite Quirk formed by the fusion of the two. This composite Quirk may sometimes give the appearance of the person having two separate Quirks, such as Shoto Todoroki's Half-Cold Half-Hot. Much more rarely, in the case of Eri's Rewind and Tomura Shigaraki's Decay, a child may manifest a Quirk that is entirely unrelated to their genetic lineage, akin to a mutation.
As Quirks are said to be the next stage of evolution in the human race, it is possible to diagnose a person as lacking a Quirk by analyzing the presence or absence of an extra joint in their pinky toe. People with only one joint will develop a Quirk while having two joints indicates that the person will not develop a Quirk.
It is possible for children to already be born with their Quirks. Such was the case with Present Mic and the very first person to manifest a Quirk, the Luminescent Baby. Although very rare, it is also possible for animals to possess Quirks, such as Nezu. Under special circumstances, two Quirks may mutate and merge, becoming a new Quirk, as was the case of One For All. It also appears that the physical mutations of mutation-type Quirks can be inherited even if the Quirks themselves are not, as people such as Fumikage Tokoyami and Koji Koda have Quirks unrelated to their appearance.
There are instances where a Quirk doesn't suit the user's body and the body can't handle it. The most obvious example is Izuku Midoriya and his Quirk, One For All. Some people, such as Yuga Aoyama, are naturally born with Quirks that their bodies can't handle. Yuga was naturally born with a Quirk that is too strong for his body and as such, he needs to wear a special belt at all times, since his Quirk would sometimes randomly fire on its own. His Quirk also hurts his stomach after using it for too long.
There are several laws and procedures to ensure the conscientious use of Quirks. During elementary school, children receive Quirk counseling, in order to learn how to use their powers responsibly. Public display of Quirks are against the law, except in cases of self-defense, such as when one is under attack or preventing someone else from being attacked.
A popular line of thinking is the idea that Quirks will continue to mix together and deepen, growing in strength and complexity with every new generation. Eventually, Quirks will develop to a point where nobody will be able to control them anymore. This is referred to as the "Quirk Singularity". This idea was first theorized by Daruma Ujiko, who started to see early signs of this back in the fourth generation, but no one, except All For One, believed his theory.
The term "Quirk Factor" refers to the collective traits that compose a Quirk. This includes the primary Quirk power as well as all the biological mechanisms that allow said primary power to function properly.
Certain Quirks such as Erasure are capable of halting the expression of the Quirk Factor, temporarily rendering the Quirk unusable, but not affecting the Quirk Factor otherwise. There are other Quirks, however, that are able to directly damage the Quirk Factor of a target, preventing the Quirk from being activated until the user manages to naturally recover. It's also implied that a Quirk Factor can be damaged beyond recovery, causing the Quirk to be permanently suppressed.
The first instance was when Eraser Head was severely injured by the U.S.J. Nomu. Eraser Head’s body sustained a large amount of damage, especially his face and head, and this caused his Erasure Quirk to have a much shorter time limit, as he has to blink more often because of the damage he took.
After initial Quirk manifestation, it is possible for the user to undergo an "Awakening". The right catalyst can cause Quirks to evolve on the spot. This results in ones Quirk gaining a new level of strength and/or new aspects to its nature that were previously not possible.
An example of this phenomenon is demonstrated when Himiko Toga's disguise Quirk evolved in a life-or-death situation, giving her the ability to duplicate the Quirks of the people she transformed into, shown when she used Zero Gravity while she had taken the form of Ochako Uraraka. It is also said that Geten's Quirk evolved when Re-Destro burned himself, from the solely manipulation of ice to being also able to change its temperature.
Known Quirk Types
Emitter (発動 Hatsudō?, lit. "Activation")-type Quirks are abilities that allow the user to generate and possibly control certain things, or alter existing things around them in certain ways. The emissions of Emitter-type Quirks can have a wide variety of properties and abilities.
Emitter-type Quirks, such as Brainwashing, Explosion, and Half-Cold Half-Hot usually require a conscious effort to activate, and some, such as Erasure, even require large amounts of concentration in order for them to remain active.
While most Emitter-type Quirks users generally have a handle on their own "emissions", it's also possible for users to hurt themselves from coming into too much contact with their Quirk. In the case of generating substances, making too much too fast or for too long can harm the user as they are using reserves from their own body, or gradually lose their natural resistance to their own harmful Quirk.
While some things produced by Emitter-type Quirks, such as the loud sound produced by Voice, have common properties, some are unique to the user, and thus have special properties, such as the ectoplasm produced by Clones. Those who alter the properties of things around them can also widely vary in effects, from molecular alteration to molecular destruction.
Emitter-type Quirks are, by a wide margin, the most common type of Quirk.
Transformation (変形 Henkei?)-type Quirks are abilities that cause the user to take on a temporary alteration of some kind. Transformation-type Quirks allow the user to temporarily "transform" their body in a variety of manners, sometimes enhancing existing features, removing features, or adding new features to the body altogether.
Transformation-type Quirks usually require a conscious effort by the user to "activate", though most users can be trained to initiate them reflexively, depending on the conditions required for activation, and practice to initiate their Quirks with greater intent and precision, such as with Edgeshot and his Quirk; he's mastered it to a point where he can change in an instant.
Transformation-type Quirks usually require a close-range proximity in order to fully utilize them in combat due to them only affecting the user's body. While Transformation-type Quirks are often quite powerful, their biggest weakness is that their effects are often temporary, and over-exertion usually leads to negative repercussions on the user's behalf. Transformation Quirks can also be limited based on the user, how resilient their body is, and the resources they have available to them (Ex. Tetsutetsu Tetsutetsu describes that his Steel Quirk softens if he doesn't consume enough Iron, and suffers from Iron Fatigue if he maintains it for too long). Some users condition their body in certain ways so that their Quirks can operate more effectively.
Transformation-type Quirks are the only known type of Quirk that can bestow the user attributes they do not normally exhibit by default. Because this type of Quirk combines the activation time and mutant-shape aspects of the other Quirk types, it is also often known as Hybrid or Composite.
Transformation seems to be the least common type of Quirk.
Mutant (異形 Igyō?)-type (also called Heteromorphic-type) Quirks are abilities that cause the user a permanent "abnormality" directly related to their power. Mutant-type Quirks create bodily structures that grant the user more complex abilities that Emitter and Transformation Quirks cannot safely provide. Often times they will bestow prehensile appendages that the user can control or add structures to pre-existing limbs to enhance pre-existing abilities. Mutant-type Quirks even have the ability to channel certain aspects of their user through them in a similar manner to Emitter-type Quirks.
Mutant-type Quirks are also the only known type of Quirk which can be passed down through generations without necessarily bestowing the corresponding ability, such as with Fumikage Tokoyami and his bird-like head that has nothing to do with his Dark Shadow, or Koji Koda's rock-like head which speaks nothing of his Anivoice Quirk. As a result of this, while it's uncertain how common mutant Quirks are, it can be safely assumed they are the most commonly inherited.
While not necessarily a weakness, Mutant-type Quirks cannot be turned off, and sometimes cause the user inconvenience due to their malformations. Such is the case with Mashirao Ojiro and his Tail Quirk, which makes it difficult for him to sit or lay down, as well as Toru Hagakure and her Invisibility Quirk, which makes it impossible to see her reflection or show up in photos. Though because these Quirks are passively-active, they are partially immune to Quirk-disabling effects such as that of Shota Aizawa's Erasure Quirk. Since Mutant Quirks are passively active they are the most identifiable at a glance.
Known Quirk Sub-Types
Accumulation-type Quirk's are powers that, in order to function properly, require the user accumulate something ahead of time, such as power, energy, mass, or a particular resource. Some such Quirks are One For All, Rewind, and Fat Absorption.
List of Quirks
List of Unnamed Quirks
|Absorption and Release||Four-Eyed Nomu||Emitter|
|Attraction of Small Objects||Inko Midoriya||Emitter|
|Fire Breath||Hisashi Midoriya||Emitter|
|Kinetic Booster||Unknown User|
All For One
All For One
|Object Gigantification||Student in red (of Seijin High School)||Emitter|
|Power Stockpiling||Unknown User|
All For One
All For One's Brother
|Sludge Form||Sludge Villain||Mutant|
|Street Line Manipulation||Ending||Emitter|
|Strength Enhancer||Unknown User|
All For One
|Tongue Web||Four-Eyed Nomu||Transformation|
|Tool Arms||Chainsaw Nomu||Transformation|
|Control Horn||Cow Cowboy||Mutant|
List of Non-Canon Quirks
|Flash Bang Sweat||Dadan Tadan||Emitter|
|Good Face||Unknown Villain||Emitter|
|Sacred Tears||Unnamed student||Emitter|
|Zombie Virus||Romero Fujimi||Emitter|