is the business-savvy, egotistical 12-year-old (13-year-old as of chapter 14) head of the English Phantomhive noble family, taking over after the deaths of his parents, Lord Vincent Phantomhive and Lady Rachel Phantomhive. He runs the Funtom Company, which manufactures toys and sweets, with the later addition of a food branch after winning a Royal Warrant His right eye, which is usually covered with a black eyepatch, bears a pentacle, the sign of the Faustian contract he made with the demon Sebastian. Sebastian says that the mark on Ciel is proof of their contract. He also says that demons mark their prey so that they can locate them.
He does not want anyone to see this mark and appears to not enjoy physical contact (possibly aphephobic), though he tolerates Sebastian and does not complain when the demon picks him up or holds him. If stressed, he will slap someone touching him away, proclaiming "Don't touch me so easily!" This is a negative influence of the trauma he underwent during his time as a slave.
He is usually portrayed as emotionless or cold, though he occasionally expresses concern for the well-being of the few close to him. He sometimes portrays himself as a happy person, mostly when undercover, but soon returns to his true self. He worries for Sebastian's well-being, but ultimately sees Sebastian as a pawn. There have been times when he wishes for Sebastian to fail at a task or request for humor's sake. He is close to his cousin and fiancee Elizabeth, seeing her as an important friend and someone he needs to protect. Before the loss of his parents, Ciel seemed to be a happy child.
Ciel seems to be highly reliant on Sebastian and does not appear to interact with other staff members as often, though they are all devoted to him. While he appears somewhat callous in the anime, such as not hesitating to throw a dart at Finnian and causing the gardener to bleed, in the manga Finnian notes that he is loyal to Ciel because Ciel does not hurt him. Ciel is proficient with the use of guns, keeping a number of concealed guns nearby in order to protect himself. He has asthma, which was inherited from his mother. He is also allergic to cats, and does not freely allow any of his staff members to keep them