Him

Him (also mentioned as "The One") is seemingly the god of all Demons and the Demon World. He is often referred to as a sort of deity. His actual name is not yet clear, but is mentioned in several instances. It is in another language, but it is pronouncable by humans.

History
1000 of years ago, he made "the promise" with the humans that demons shall no longer hunt humans. After a certain time period, the demons celebrate and offer their prayers to Him. This feast is called the Tifari and involves offering only the best meal to Him.

Appearance
The One has a small, rather child-like appearance. He's dressed in somewhat royal garments along with a cloak. His head consists of a skull with large horns. In the middle, He has one eye surrounded by three star-like markings. He is also able to take on a more humanoid and adiult appearance.

Personality
Not much is known about Him. He seems quite calm and very knowledgeable. Him wanting to "play" with Emma might show that He possesses a somewhat playfully twisted nature, where He enjoys toying with humans. He does appear somewhat friendly and not hostile. However He still gets serious and has his own demands.

Introduction Arc
Yverk is pleased by the information that Grace Field's premium children, Emma, Ray and Norman, are able to be shipped out. He states how everything must be ready and perfect for the Tifari. The premium children shall be offered, 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.

Search For Minerva 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 here, 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 her group left Cuvitidala, Him appeared behind them as he watched the children leave.

Cuvitidala 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/worm 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 Cuvitidala flies down and He emerges. He also shrinked from a more humanoid form into his regular small appearance. He explains to Emma how Ray was unable to enter the place because his own mind was too centered around logic and he couldn't break free like Emma did, This is what makes Him remark to Emma (that she must be very delicious). Emma then asks Him to reforge the promise. He simply says "OK", much to her surprise. Nevertheless, Him still requests a reward in exchange from Emma, just like 1000 years ago.

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".