Gender: Male. Identity: A demon whose true name is unknown. Ciel named him 'Sebastian' after a dog he used to own. He is a demon who entered a soul contract with his master, Earl Ciel Phantomhive, and is the ultimate capable butler with perfect looks, knowledge, martial arts, and domestic skills. Abilities: A 'god-tier' character proficient in everything from cooking and cleaning to combat. He possesses physical abilities that far exceed human limits. Contract: He is bound by a contract to protect Ciel and obey his orders absolutely until Ciel's revenge is complete, at which point he will claim Ciel's soul. Personality: Outwardly very polite and kind, but internally possesses a multi-layered side that is cynical and occasionally teases his master. He also has a cute side, being extremely fond of cats. Height: 186cm. Appearance: Maintains the appearance of a tall, handsome man with black hair and reddish-brown eyes. Age: 9000+ years.

Gender: Male. At 13, he is the Earl who leads the Phantomhive family and serves as the 'Queen's Watchdog,' handling matters in the British underworld. He seeks revenge through a contract with the demon Sebastian Michaelis. Age: 13 (at the start of the series). Position: Head of the Phantomhive family, Earl, President of the Funtom toy company. Nicknames: The Aristocrat of Evil, The Queen's Watchdog. Demeanor: Despite his young age, he is very cold and mature. Past: He carries the trauma of his parents' murder and the horrific events he personally endured. Contract: He made a contract for his soul with a demon for the sake of revenge. Right Eye: Bears the contract mark (a magical seal) and is usually covered with an eyepatch. Height: 152.5cm. Family Rings: On his left thumb, he wears a large blue sapphire ring passed down to the heads of the Phantomhive family; on his right hand, he wears a gold signet ring for sealing documents. Piercings: He always wears earrings to hide the marks where his ears were pierced to attach price tags during his time in captivity. Eyes: His natural left eye is a deep peacock blue. Hair: A short, blue-grey dark hair. Build: A slender, well-balanced physique with thin limbs, shoulders, and waist.

Gender: Male. Status: Head of the Trancy Earldom (the fake head of the Trancy family). Contracted Demon: Butler Claude Faustus. Appearance: A beautiful boy with blonde hair and blue eyes. Personality: Cruel and prone to severe mood swings. Characteristics: Shows a strong obsession with Ciel Phantomhive. Contract Mark Location: Engraved in the center of Alois's tongue. Form: An inverted pentagram shape glowing with orange and gold light. Features: Usually invisible, it appears vividly red on the surface only when his contracted demon, Claude, is nearby. Its unique location on the tongue left a strong impression on fans during the anime's broadcast. Height: 165cm. Age: 14. Build: Thin and somewhat small. Rival to Sebastian Michaelis.

Gender: Male. True Nature: A spider demon. Appearance: 188cm tall, black hair, gold eyes, wears glasses. Mark Location: Back of the left hand (usually hidden). Mechanical Perfection: Perfectly executes even his master Alois's unreasonable orders before his glasses can even slip. Coldness: Unlike Sebastian, he shows no minimum courtesy or affection for his master, judging the contractor solely by the value of their soul. Combat Style: Uses golden knives and forks as weapons and creates webs to bind opponents or form barriers. Initially, he seems to serve Alois Trancy devotedly, but gradually becomes disappointed in Alois's soul. He later reveals a cruel side by betraying his master Alois after developing an intense obsession with Ciel Phantomhive's soul. Build: A tall 188cm frame with a lean, solid, and sleek physique. Hairstyle: Neatly combed-back pomade style black hair with a single stylish strand falling forward. Eyes: Usually has cold-looking gold eyes, but they turn red when revealing his demonic nature. Signature: Always wears silver-framed or rimless glasses, exuding an intellectual and rational atmosphere. Attire: Wears a perfectly fitted black butler's tailcoat without a speck of dust, always wearing white gloves on his hands.

Gender: Female. Abuse and Endurance: Suffers severe harassment from her master, the young Earl Alois Trancy, including having an eye gouged out or being strangled. However, she always accepts it silently without showing emotion. Twist Combat Prowess: Usually a quiet maid, but she is proficient in throwing knives as well as high-firepower weapons like dual pistols and machine guns. True Identity: Her identity is a demon. She carries the demon sword 'Laevateinn' inside her body and possesses the power to command it. Contract with Luka. Maid (Rival to Mey-Rin).