What Are Quirks?

In the anime and manga series My Hero Academia (MHA), Quirks are superhuman abilities that roughly 80% of the world's population possess. First appearing generations ago, these powers transformed society and led to the rise of both heroes and villains.

Quirk Characteristics

Genetic Origin

Quirks are a biological and genetic part of a person, often inherited from their parents. In some cases, a child's Quirk can be a mix of their parents' abilities, as seen with Shoto Todoroki's "Half-Cold Half-Hot" Quirk, a combination of his parents' powers. Though, Midoriya’s Quirk is an exception to this rule, having been handed down by All Might.

Unique Manifestation

A Quirk typically appears in a person by the age of four. While they are usually unique to the individual, some are more common than others.

Physical Toll

Overusing a Quirk can result in negative side effects on the user's body. The severity of the drawback depends on the Quirk's nature; for example, Denki Kaminari becomes mentally incapacitated after exceeding his electrical output, while other characters might experience temporary fatigue or nausea.

Evolutions and Awakenings

With intensive training, a Quirk can grow stronger, similar to how muscles develop. In rare cases, a user might experience a Quirk Awakening, which can cause a significant jump in power, often triggered by intense trauma or extreme circumstances.

Types of Quirks

In the MHA universe, Quirks are generally categorized into three types based on how they function.

Emitter

Users can generate and control specific substances or energy, such as explosions, electricity, or ice. They typically require a conscious effort to activate.

Examples: Katsuki Bakugo ("Explosion"), Shoto Todoroki ("Half-Cold Half-Hot"), and Ochaco Uraraka ("Zero Gravity").

Transformation

These Quirks cause a temporary alteration of the user's body, usually for close-range combat. Their effects often wear off with overuse, causing strain on the user. 

Examples: Eijiro Kirishima ("Hardening"), which allows him to make his body rock-hard for offense and defense.

Mutant

These Quirks create a permanent, physical mutation or abnormality in the user's body, which cannot be turned off. They are always "active" in a sense, giving the user complex abilities.

Examples: Fumikage Tokoyami ("Dark Shadow"), who has a bird-like head and can summon a sentient shadow monster, and Mezo Shoji ("Dupli-Arms"), who has multiple arms.

Notable or Rare Circumstances

Accumulation

A very rare sub-type of Quirk that accumulates something over time. One For All is the prime example, stockpiling immense power and the Quirks of its previous users.

Sentient Quirks

In extremely rare cases, a Quirk can manifest as a sentient being linked to the user. An example is Fumikage Tokoyami's "Dark Shadow". 

Quirkless

Not every person has a Quirk. Historically, the entire population was Quirkless, and even today, about 20% of the population is born without a Quirk. The protagonist, Izuku Midoriya, was born Quirkless before inheriting the One For All Quirk.