Quirks are the collective term used to describe the abilities the inhabitants of His'kilooi Earth started showing approximately 2206 NE. Appearing suddenly all across the planet in a way that's distinctly similar to how Conduits started appearing on Gol'kkiler Earth. However, this was affecting far more percentage of the population, nor did it require an external force to active these abilities which at first confused researchers of the Allied Organization of Health. Not to mention just how random these Quirks were, ranging from reasonable (telepathy) to absurd (organic earphone connectors).
Overtime however, it's soon discovered that the inhabitants of His'kilooi Earth that showed those who held these 'Quirks' had DNA structure that resembles the characteristics of someone infected with either a Retrovirus (ex. Forced Evolutionary Virus) or a mutagenic virus (which is what caused the Klingons to develop a more Human-like appearance). This caused even further research to the DNA of the planet's population and discovered the reason for the quirks sudden appearance.
Finally, after five years of research, the Allied Organization of Health finally discovered the source of the Quirk's development. A Virus created by the First Human Empire during the Second Human Civil War that was developed to become the ultimate bioweapon, becombing the characteristics of a retro-virus and a mutgenic virus into one. However, something occur and caused the Virus to develop sentience and spread out of control, forcing the Fist Human Empire to contain the virus on the planet where it remained dormant for untold eons. Until something awoke it and caused it to spread, but for some reason, the virus's monstrous sentience didn't come back but the virus unknowingly spread across the planet and infecting everyone, mutating their DNA until it finally developed into the Quirks now commonplace on the planet.
The first person to manifest a Quirk was a newborn baby in the city of Quig Quig, China, who had the ability 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 spread of a virus carried by mice had brought about their development. As of 2416 NE, more then 80% of the planets' population possesses a Quirk.
At the dawn of this extraordinary era, 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, heroes, began to exist. 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.
Quirks are inherited genetically and typically manifest in children by the age of four, at the latest. Children will either manifest one of their parent's Quirks or if the two are compatible, 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's Half-Cold Half-Hot. Much more rarely, in the case of Eri's Rewind, a child may manifest a Quirk that is entirely unrelated from 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 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".
Quirk Factor Edit
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 activation process 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 inoperative.