Justice Devil

The Justice Devil (の) is a Devil that embodies the fear of justice. They are the unseen overarching antagonist of the titular Justice Devil arc.

Appearance
The Justice Devil's true appearance is unknown.

Personality
Nothing is known about the Justice Devil's personality, except that they tend to contract with anyone who sees their actions as "right" and "justifiable" (such as the class president and Yuko) regardless of the actual morality behind their actions. It also apears to ask for nothing in return when making contracts which could be seen as benevolent.

History
At some point the Justice Devil took up residence at Fourth East High School, beginning to make contracts with its students. It's unknown how many students they have previously contracted with, but one of them was the class president. The class president made a contract with the Justice Devil because she was jealous of her classmate, Asa Mitaka for capturing Mr. Tanaka's attention due to her aloofness, and the lack of socialization in their class. Mr. Tanaka was also having an affair with the class president, but it's unknown when it started.

Justice Devil arc
On her way to visit Bucky's memorial along with Mr. Tanaka and Asa, the class president uses the contract to transform into a being made of muscle and attempt to kill Asa. The class president is later killed along with Mr. Tanaka by the War Devil after taking Asa's body.

Later, Yuko also makes a contract with the Justice Devil, which allowed her to read Asa's mind. After being defeated by Chainsaw Man, Yuko later warns Asa that the Justice Devil is still at Fourth East High School, possibly having made contracts with other students.

Abilities
As a Devil, the Justice Devil possesses all of the standard devil abilities. These include the ability to make contracts with humans. The contracts with it seen so far are those with the class president and Yuko. Unlike the other devils, the Justice Devil seems to ask no price in exchange for their contract; Yuko tells Asa that the price for her contract is only to receiving "a heart that shines with justice".

Devil Powers
Mind Reading: Seeing as Yuko received this ability from the contract it can be assumed the the Justice Devil also possesed this ability. The Justice Devil can read the mind of anyone as well as their memories.

Justice Empowerment: The Justice Devil can transform the sense of justice of anyone who contracts with him into power. This power seems to vary according to the sense of justice who made the contract:


 * The contract with the class president, who wished to have a happy ending with her teacher, gave her the power to transform her body into a blob of flesh with multiple heads, large muscular tentacles with claws-like fingers and superhuman strength. While in her transformed state, she is able to move very quickly, being able to attack in just seconds and she was capable to slice though Asa Mitaka's skull and flesh, killing her nearly instantly.


 * The contract with Yuko, who wished to punish the bullies who persecuted Asa Mitaka, gives her the ability to read others' minds and detect their inner thoughts and feelings. The contract also allows Yuko to transform into a thin and gaunt being with an uncovered brain and tentacles instead of legs.

Trivia

 * The Justice Devil is based more on one's own personal sense or “idea” of justice rather than actual justice itself. The transformation of the class president shows numerous heads, as if to symbolize that the idea of justice has "many faces", varying according to each person's personal perspective.
 * The price of the contract with the Justice Devil ("a heart that shines with justice") is likely to be some part of the user's personality or understanding of right and wrong to be altered. As shown, the personalities and sense of right and wrong of Yuko and the class president appears to have been grossly and unknowingly altered, deformed or radicalized by the Justice Devil as the actual "price" for their powers.
 * Asa originally speculated that Fami was the Justice Devil, which is a reference to how Famine is sometimes interpreted as the "Lord as a Law-Giver."
 * Both famine and Justice are often represented by scales.