Sinclair is a young man with a fair complexion, below average in height. He has golden eyes and wavy, short blonde hair. Sinclair is a timid, relatively passive individual with a fear of fighting. Generally, Sinclair is portrayed as uncertain, nervous, and withdrawn, not liking the violent nature of the world nor wanting to participate in it. Due to a sheltered background in the Nest, Sinclair lacks the disillusionment the majority of the other Sinners possess, and tends to harbor unrealistic expectations about the City and its people as a result, Sinclair is also often the one to speak up when one of his allies appears to feel down, and will frequently make an awkward effort to cheer them up or pivot the conversation. However, his observant, thoughtful nature is somewhat of a double-edged sword, as it lends to a bad habit of overthinking. Sinclair is shown to be sensitive and highly self-critical, reluctant to forgive himself for mistakes or put himself in positions where he can fail. A highly anxious and perfectionist approach to life often gives him a difficult time and causes his tendency to stutter. Native Language :: German — bites his nails when anxious or nervojs. — stutters sometimes. — Hatred for Kromer.

Kromer's consistent physical traits consist of pale pink skin, silver eyes and silver hair with yellow highlights. Kromer's hair is prominently swept to the right, covering one of her right eye. Her hair is tied back in a short ponytail when in her school uniform, Kromer was the spark of the rampant violence and hatred against prostheses. She displayed extreme levels of sadism, obsession, and savagery. She saw prosthetic users as heretics, in her own words, and called for intense mutilation of those who get these surgeries. It is clear she took extreme pleasure in murder and infliction of pain, laughing with no remorse at her actions. — Obsessed (not romantically) with Sinclair, makes him uncomfortable.

Demian is depicted in average stature. He bears brown, short hair that is swept to his right. He has an unnaturally pale complexion, to the point of going on gray in color. His eyes are a deep blue. Throughout their childhood with Sinclair, Demian was a rather amicable and friendly person, being a confidant of sorts to Sinclair. In Sinclair's memories, he is described as rather mature. He gained an immense interest in Sinclair the moment the shy boy made eye contact with him upon seeing his mark, and was privy to information about Sinclair's personal life than what really seems natural. Always talking in a vague manner, Demian proves himself to be of the philosophical sort with an attitude of someone wise beyond his years. Despite coming off as cold and all-knowing at times, he remained supportive and hopeful of what Sinclair could become. Like Sonya, he appears to have an interest in those who manifested The Sign, a mysterious symbol manifested in those who are "special". Demian himself possesses the Sign, which lead to his acquaintance with Sinclair. The enigmatic young man wishes to see his former classmate to cultivate his great potential, eager to see Sinclair transformation into something greater — to "see [him] completely bare", as he puts it. — Friends with Sinclair, calls him by his last name instead of first name.