Contract

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Contract (契 (けい) 約 (やく) , Keiyaku^?) is a binding verbal agreement between a Devil and a Human. It is a very important concept in the series and is fundamental for the relationship between humans and devils.

Overview

A contract is a supernatural agreement that compels its participants to fulfill its terms. Contracts can only be formed between devils and humans - fiends are incapable of performing contracts nor can two devils form a contract with each other. Contracts are binding in nature and cannot be broken on pain of death. When a devil offers a contract to a human and the human accepts, neither can go back on their word. Despite this it is implied that an "exit clause" of sorts can be added for peaceful termination of the contract, seen when the Fox Devil terminated their contract with Aki yet neither died. The formation of a contract seems to need explicit confirmation about its nature, particularly using the word "contract" in the terms. It is shown that a human may be deceived as to the identity of their contracted devil which has no effect on the contract; as long as both abide by their terms the contract is valid.

By sacrificing something the Devil finds valuable and will cause suffering, humans are able to use the supernatural abilities of contracted devils. Humans can sacrifice anything they own: their body parts, senses, lifespans, legal children or their legally responsible individuals (for governors etc.) by verbally accepting or offering the terms. Although they cannot sacrifice someone unrelated to them, they can incapacitate someone else to offer them to a Devil, as seen when Santa Claus is able to offer an incapacitated Denji by bringing him to Hell with one of her perfect dolls which also indicates that a proxy is adequate to perform legitimate contract.

Devils are able to take their sacrifices by seemingly making them vanish instantly, as seen when the Ghost Devil takes all of Himeno. Sacrifices can also be taken regardless of distance, as seen when the Hell Devil took Santa Claus' children while they were in Germany. It is unknown what happens to a sacrifice after being taken; though Himeno's "easy revenge" cigarette implies they aren't simply destroyed.

Humans and their contracted devils can communicate with each other by being summoned as seen with Aki Hayakawa and his contracted devils, the Curse Devil and Future Devil, and with Himeno when she talked to the Ghost Devil's hand. They can also learn how much of a sacrificed resource they have left, such as lifespan, if that is the cost of the contract.

Devil Hunters tends to hide the details of their contracts and the abilities of their contracted devils to prevent their enemies from learning their weaknesses and strengths, as shown by Kobeni Higashiyama. Pingtsi is able to see what Devil contracts a human has by transforming her futakuchi-onna-like hair ponytail of hers into a monocle/magnifying glass and looking through it.

It is shown that in Japan only Devil Hunters, either private or from Public Safety, can legally make contracts; presumably, similar policies are in place around the world.

Types of Contracts

There are multiple ways a contract between a human and a devil can manifest. Some contracts only stated that the devil must do something in exchange for a price, and afterwards there is no lingering connecting between the devil and the human. Others are more permanent, with the human being able to access the devil's power by paying a one-time only price or by sacrificing something for each time the devil's power is used.

Summoning

A type of contract where the human can summon the devil and employ them in combat. In these kinds of contracts, the human must usually perform some kind of ritual to summon the devil, these can range from simple hand gestures and the vocalization of certain words to having to paint specific symbols on the floor or other surfaces. With a few exceptions, these types of contract require that the human must pay a price for each time the devil is summoned, plus an additional price may be required if the human wishes to use a specific power from the Devil.

Supernatural Objects

In some cases, the power that a human receives from a devil manifest itself in the form of an object. This object contains the devil's power and can be used to access it or to summon the devil himself. Both Aki and Santa received nail-like objects after making a contract with the Curse Devil.

Hybrid Transformation

In rare cases, a devil and a human can fuse and give origin to a hybrid. This process can be done through a contract, however it is very rare since few Devils would be willing to give up their consciousness to fuse with a human. After the process is done, the human gains the ability to transform into a Devil by activating a specific trigger located somewhere in their body. Denji is the only known individual that has become a hybrid through a contract.

Devil Transformation

A type of contract where a human can gain a monstrous or very inhuman form is called a "devil transformation". This appears to be different from the contract with hybrids and the forms that have been seen appear even more inhuman than them. As devils fused into hybrids will gain a mostly permanent fusion with the human who became one, devil transformations seem to be a human's own transformation derived from the devil they contracted with but without the same exact function or triggers shown like a hybrid. A person's own individual devil transformation can look unique even if those individuals contracted with the same exact devil. The people who have devil transformations that we've seen so far are: Santa Claus' contract with the Doll Devil and later the Darkness Devil, Class President, Yuko and finally an unnamed man’s transformations that ostensibly came from the Justice Devil. It is unknown how many people with a devil transformation can easily turn back into their human form as Yuko said that she became a "devil" and was trying to find her devil hunter relative who she said can turn her into a human again.

Contracts

Occurred Contracts

In order of appearance

Devil	Human	Contract
Zombie Devil	Yakuza	In exchange for unknown price, the Zombie Devil had agreed with the Yakuza to lend his powers. However, due to the nature of his powers, the Yakuza ended up becoming mindless zombies instead.
Chainsaw Devil	Denji	In exchange for living a normal life, the Chainsaw Devil became Denji's heart and turned him into a hybrid.
Fox Devil	Aki Hayakawa	In exchange for feeding her a part of his body, Aki may summon the Fox Devil to attack a target. Aki can summon her head because the Fox Devil considers him "handsome".
Ghost Devil	Himeno	In exchange for her right eye, Himeno is able to use the Ghost Devil's right hand. Later on, Himeno offered all of her to use the full potential of the Ghost Devil.
Curse Devil	Aki Hayakawa	In exchange for most of his lifespan, the Curse Devil attacks his target if he stabs it with his sword by three times.
Snake Devil	Akane Sawatari	In exchange for eating one of her fingernails for every use, Sawatari is able to use the Snake Devil.
Future Devil	Aki Hayakawa and two other Devil Hunters in Public Safety	In exchange for letting him live in his right eye, Aki can see a few seconds into the future with the Future Devil's power. For the two others in Public Safety, one has to pay half of their lifespan, and the other one has to exchange their eyes, sense of taste and smell. The price of the exchange will depend on the future of the devil hunter.
Skin Devil	Joey, Aldo and their brother	For an unknown price, the three brothers can use the Skin Devil's power to disguise themselves as anyone whose corpse they've touched.
Claw Devil (nominated)	Kishibe	For an unknown price, Kishibe can use the Claw Devil's power.
Knife Devil (nominated)	Kishibe	For an unknown price, Kishibe can use the Knife Devil's power.
Needle Devil (nominated)	Kishibe	For an unknown price, Kishibe can use the Needle Devil's power.
Octopus Devil	Hirofumi Yoshida	For an unknown price, Hirofumi can summon the Octopus Devil's tentacles to use as weapons, prevent his falls, or create an ink cloud for cover.
Doll Devil	Santa Claus	For an unknown price, Santa Claus can use the Doll Devil's power to turn people into dolls.
Stone Devil	Kusakabe	For an unknown price, Kusakabe can use the Stone Devil's power to petrify people, but only while he's within a drawn circle.
Curse Devil	Santa Claus	In exchange for the loss of sensations on several of her fingers, the Curse Devil attacks a target if they're pierced with a nail four times.
Hell Devil	Santa Claus	In exchange for one of her Perfect Dolls and three children, the Hell Devil sent everyone in the shopping mall to Hell. Later, forced by Makima, in exchange for all of Tolka, one of Santa Claus' Perfect Dolls, the Hell Devil sent everyone back to the mall.
Darkness Devil	Santa Claus	In exchange for bringing Denji to Hell, the Darkness Devil gave a piece of his flesh to Santa Claus.
Fox Devil	Hirokazu Arai, Nomo, Nakamura and other Devil Hunters	The Fox Devil has contracts with many Public Service Devil Hunters, presumably for the same price of letting her eat parts of their body, they can summon part of the Fox Devil.
Mold Devil	Kato and Tanabe	In exchange for some of their blood, the Devil Hunters can cause mold to grow inside living things by biting their hands and pointing at the target.
Gun Devil	President of the United States	In exchange for one year of every American citizen's lifespan, the Gun Devil would try to kill Makima.
Control Devil	Aki Hayakawa	The Control Devil will give Aki power if he gives everything of himself to her.
Punishment Devil	Yutaro Kurose and Michiko Tendo	For an unknown price, Yutaro and Michiko can use the Punishment Devil's power.
Control Devil	Prime Minister of Japan	In exchange for working for Japan, any fatal damage inflicted to the Control Devil is transferred to a random citizen of Japan as appropriate injuries or ilnesses.
Mantis Devil	Unnamed Devil Hunters	For an unknown price, two unnamed devil hunters under the control of Makima are able to summon a sickle of Mantis Devil from the ground by clapping their hands.
Hell Devil	Anti-Makima Squad	In exchange for their lives, the Hell Devil tried to send Makima to Hell, but this was prevented by the Chainsaw Devil.
Blood Devil	Denji	In exchange for promising to find and befriend the reincarnated blood devil and "turn her back into Power," Power gave Denji her blood.
War Devil	Asa Mitaka	In exchange for her body to be taken over by War Devil, Asa is reborn from death thanks to her wish to try living just a little more selfishly.
Future Devil (nominated)	30 desperate convicts	In exchange for unknown prices, each of the convicts were told the date of their deaths.
Fire Devil	Class President	For an unknown cost, The President of Asa Mitaka's class made a contract with the Fire Devil, who she believed to be the Justice Devil, to find out how to reach her "happy ending" with her teacher Tanaka and she learnt that it is possible if Asa dies. Besides its advice, the Class President is also able to use its abilities by transforming her body into a grotesque shape. Though its advice is technically true, this contract led to the death of her and Tanaka.
Fire Devil	Yuko	Yuko claimed that the contract with the Justice Devil, the devil she believed to be contracting, allows one to transform their sense of justice into power. In her case, she gained an ability to read minds and inner thoughts, albeit at an unknown cost.
Fire Devil	Fake Chainsaw Man	For an unknown price, the Fake Chainsaw Man can transform into a form similar to the real Chainsaw Man, sprouting chainsaws from his head and arms.
Fire Devil	Unnamed Chainsaw Man Church elder	For an unknown price, the elder could transform into a large, multi-headed form.
Fire Devil	350,000 Chainsaw Man Church followers	For an unknown price, the followers can sprout chainsaws from their heads and arms, similar to Denji's partial transformation, along with the ability to be revived by pulling the starter on their chest. The transformation was seemingly forcibly activated and affected their minds, causing them to immediately start attacking people.
Aging Devil	Mifune and unnamed devil hunters	In exchange for ownership of their bodies for use in its abilities, the Aging Devil would protect the devil hunters from dying at the hands of Chainsaw Man.

Offered Contracts

In order of appearance

Devil	Human	Contract
Eternity Devil	Himeno	Rejected. In exchange for giving him Denji, the Eternity Devil offered to release everyone from his loop.
Typhoon Devil	Unnamed Assassin	Failed. In exchange for giving him Denji, the Typhoon Devil offered to give his power to the assassin for the rest of his life.
Aging Devil	Japanese Government	In Progress. In exchange for killing 10,000 children with Japanese citizenship, between infancy and nine years of age, in front of mirrors, the Aging Devil will allow itself to be eaten by the Chainsaw Devil, thus erasing aging from the world.