Him

Him (彼, Kare), also referred to as "The One" (それ, Sore) or his real name, "", is seemingly the absolute ruler of all Demons and the Demon World, worshiped as a deity. Top-grade children from the Premium Farms are sacrificed to him during a festival called Tifari. His actual name always written in Demon script in the text, but is mentioned in several instances and is pronounceable by humans.

He lives in a special dimension where the laws of time and physics do not apply; said to be located in a mysterious space with a dragon. Anyone who wishes to contact Him must go through a special ritual and trial that involves strange metaphysical puzzles. Unlike the other Demons, Him is very special and has unique powers that allows him to control the Demon world and its setting.

History
His origins are unclear, but he is considered deity-like by the demons, and was the one capable of making Promises on their behalf. Initially due to his powers, Him was regarded in fear by the other demons and treated as an outcast. However, over time the perception of Him changed, and demons raised him as a god.

1000 years ago, He made the deal with Julius Ratri that became known as the Promise; the demons and humans would be partitioned between two worlds, unable to access one another. The Human World would be free of demon predation, and in exchange the demons would be allowed to farm the humans stranded on their world. The Ratri Clan additionally were tasked with maintaining the promise, with Julius Ratri forced to stay in the Demon World. For the Demon's, He declared the Tifari, a celebration in which the very best of all the children from the Premium Farms will be offered to Him.

Appearance
He is small, with a child-like appearance. He is dressed in regal clothing with a hood. His head consists of a skull with large horns. In the middle, He has one large green eye surrounded by three star-like markings.

He is also able to take on a more humanoid and adult appearance, implying his form is a matter of choice than necessity.

Personality
While his full nature is unknown, he is shown to possess a playful, alien and possibly sadistic nature. While seemingly disinterested in devouring humans as a first response, he was the one who established the Promise and thus the system of Human farming, and shows neither remorse nor concern for the humans plight, or the mental suffering afflicted upon Emma and Ray as they passed through the Seven Walls and left them in despair, confusion, and fear of the unknown.

The exact motivations and need of Him are unknown, though his actions may simply be a method of entertaining himself. He is not hostile when meeting either Emma or Julius Ratri, but displayed seriousness when it came to exact his price and the requirements of his promises. Seemingly, all that is needed to cause him to allow a new Promise to be made is reaching him; when Emma expressed her desire to free all the cattle children, He responded with a simple "okay".

In contrast, in exchange for creating his Promise, He demands a specific payment that he will not reconsider. The payment one must give up is the thing that is most important to them. For Yverk and the Demon Queen, it was the most valuable human meal of the year, to prove to her she will never be his superior. For Julius, it was his freedom and comrades who became humanity's first cattle. Julius was forced to be the guardian of the Promise in the Demon World for the rest of his and his families lives, ensuring he could never be free of his pain and especially not his guilt. For Emma, it was her family, but per the conditions of Emma's Promise, all of the orphans must be sent to the Human World meaning He could not kill Emma or her family or keep them in the Demon World, so instead he took all of Emma's memories of her family and transported her to a different part of the Human World than everyone else.

Skills and Abilities
Along with the typical skills and abilities that all demons possesses such as a long lifespan, invulnerability and regeneration, also possesses these unique skills and abilities:

Essokinesis: He has the ability to defy physics and control reality.

Omnikinesis: He has the ability to control anything and everything that exists in the Demon World and in other dimensions like the Seven Walls and Day and Night.

Omniscience: He is seemingly all knowing.

Chronokinesis: He can control time and space.

Teleportation: He can teleport people from the Demon World to the Human World as seen with the Factory Farm orphans in chapter 178.

Visions: He has the power to give people visions of anything they want to see.

Hallucikinesis: He created many different illusions and puzzles for Emma and Ray to solve in the Seven Walls.

Levitation: He can levitate above the ground.

Age Manipulation: During his "game" with Emma and Ray in the Seven Walls, they both became younger and then older.

Shapeshifting: He can change is appearance between at least three different, but similar, forms including a short child-like appearance and a tall adult-like appearance.

Telepathy: He can talk to Emma seemingly through her thoughts.

Introduction Arc
Yverk is pleased by the information that Grace Field House's top three "premium quality goods", Emma, Ray and Norman, are ready to be shipped out. He states how everything must be ready and perfect for the Tifari. The "premium quality goods" shall be presented as an offering, as he evokes his prayers to Him.

Jailbreak Arc
When Emma and Norman talk to Krone and asked her about information, Krone questioned whether they know about Him. They were confused and she promised to tell them next time.

Promised Forest Arc
The children expressed their plans to break the Promise. Mujika says they'll make an enemy of The One but Sonju said that He was their enemy from the start.

Cuvitidala Arc
When Emma, Ray, Violet, Zack, Don and Gilda arrived at Cuvitidala, Emma noticed odd markings on the stones. After touching them, she is transported to another realm and has visions of the past. She also meets Him there. He is surprised by her appearance and tells her that there is nothing there, yet at the same time everything. Before Emma could confirm if He really was Him, He said, that it's time to play and sent her back to the Demon World to the others. As Emma and the group left Cuvitidala, Him appeared behind them as he watched the children leave.

Seven Walls Arc
Emma wants to reforge the promise with Him and make a new one, so that humans and demons can finally live in peace. She and Ray perform the ritual to enter His realm. They end up in a strange world, where He is seemingly able to manipulate space and time. But it turns out that the realm is influenced by their conscious and subconscious minds. In this strange world they found a four-dimensional hypercube with a pitch-black spherical opening that looks like a black hole. Emma is sure that this object is the gate to reach Him. Emma and Ray grab their hands and decide to touch the black hole-like object.

After this, Ray is teleported back to the shelter while Emma meets Him in "the place of night and day". There, the dragon flies down and He emerges. He first appeared with a tall slender humanoid form, before shrinking down into into a smaller child-like form. He explains to Emma how Ray was unable to enter the place because his own mind was too centered around logic and he could not break free as Emma did. Emma then asks Him to reforge the Promise. He simply says "OK", much to her surprise. Nevertheless, He still requests a reward in exchange from Emma, just like 1000 years ago.

Human World Arc
The reward Emma was required to give Him in exchange for her Promise is not revealed until the Human World Arc. After rescuing her friends from Grace Field, Emma tells the other children that He did not request a reward from her. However, after arriving in the Human World, the other children discover Emma was lying as she was not transferred to the same location as the rest of them. In a flashback it is revealed that He wanted Emma's family as his "reward" for her Promise. However, per the conditions of Emma's Promise, all of the orphans must be sent to the Human World, meaning He could not kill Emma or her family or keep them in the Demon World, so instead he took all of Emma's memories of her family and transported her to a different part of the Human World than everyone else.

Trivia

 * In the manga, when the characters such as Yverk, Emma and Krone mentioned the demon, he is referred to by his name in the demon language, . In the anime, however, was referred to as "Him".
 * Shirai, Sugita, and Posuka call the demon "marumaru sama" (beep-beep-sama, roughly). Once, the pronunciation of 's name was decided, Sugita asked Shirai how to say his name for the dialogue in the anime. Shirai thought for a few hours and decided on the pronunciation, but it was not used, instead opting to refer to simply as "Him".
 * The written form of his name was decided by Sugita. He combined "S" and "D" (for "Shirai" and "Demizu") from ancient letters and turned them over, then added a line above to determine top and bottom. Sugita made it quickly, and he thinks if readers want to decipher it, they would be able to.
 * Sugita wanted to use an unusual font for his quotes. Shirai didn't know the name of the font, so he used to call it "Voice of Terada Kokoro kun font". He light-heartedly apologizes to the child actor for using his name without permission.