BoC Ciel's contract eye

Ciel's contract seal.

A Faustian contract or a deal with the devil,[1] is a link and bargain between a human and a demon whereas the latter offers specific services and fulfills the human's wish, and is rewarded the human's soul after the contract is complete.


Creating a Contract

In order to create the contract, a human has to summon a demon. However, it seems that they do not need to be aware of the existence of demons, attempt to summon a specific demon, or even summon one intentionally, as Ciel Phantomhive states he summoned Sebastian Michaelis accidentally.[2] It is implied that the human must be desperately searching for a way out, if Ciel's situation is indicative of a typical summoning process, and have little or no faith in God. Sebastian states that once summoned, this fact will not change for all eternity. All the same, it seems that the human still has the option to go through and create the contract, or dismiss the demon, as when Sebastian was summoned, he asks Ciel to make a decision.[3] However, the creation of the contract is finalized as soon as the human issues a command to the demon.[4][5]

Contract Seal

Placing the contract

Sebastian placing the mark on Ciel.

Once the contract forms, a seal is placed on the human's body (e.g. Ciel's seal is on his right eye and Sebastian's is on his left hand). Sebastian has likened the contract to a "collar."[6][7] It is absolute; just as the demon is able to find the human, the human can never escape.

Demon contracts

The different contract seals as seen in the anime. Top is Sebastian's, middle is Claude's, bottom is Hannah's.

The demon is able to place the seal on the human by simply pressing their hand against the chosen place. The choice as to where the seal resides is up to the human, since Sebastian had asked Ciel where he wants the seal to be located. The more visible the seal is, the stronger the bond is. The placing of the seal is also painful.[8]

In the anime, it is shown that each demon has a Contract Seal design specific to themselves.

Standard Practice

If the human's wish is not yet fulfilled, the usual practice for a demon is to serve under the human for as long as it takes and to perform supplementary orders; Sebastian serves as Ciel's butler. The demon is to protect and be the human's power. It must obey the orders the human gives, as long as the contract is still in effect.[9]


Once the contract is complete and the human's wish is achieved, the demon will eat the human's soul, which results in the human's death.



  1. Wikipedia:Deal with the Devil
  2. Kuroshitsuji manga, Chapter 36, page 13
  3. Kuroshitsuji manga, Chapter 19, pages 10-11
  4. Kuroshitsuji manga, Chapter 19, page 12
  5. Kuroshitsuji manga, Chapter 11, page 29
  6. Kuroshitsuji manga, Chapter 8, page 5
  7. Kuroshitsuji manga, Chapter 26, page 29
  8. Kuroshitsuji manga, Chapter 62, page 4
  9. Kuroshitsuji manga, Chapter 13, pages 26-27