Atsushi Nakajima

Atsushi has light gray hair, pale skin, and is of average height with a slim build. He has segmental heterochromia, consisting of purple on the top half of his iris and yellow along the bottom curve of his pupil. His hair is short and swept forward in loose spikes with a lock left long on the right side of his face. This uneven style is the result of bullying he suffered at the hands of other orphans in the orphanage, and he never fixed it. Additionally, he has a prominent black streak in his hair.

Atsushi's traumatic past affects much of his daily life, and he is tormented with nightmares, flashbacks, and the internal monologue of the orphanage director who abused him.He has a severely low sense of self-worth and is somewhat naïve, which causes him to initially feel helpless when confronted with dangerous situations. When paralyzed in guilt and/or fear, he has difficulty reacting or understanding what to do

All things considered, Atsushi cares deeply for his fellow Agency members and for the well-being of civilians, especially during dire situations. On various instances, Atsushi would not hesitate to help and save others, even those he has never met before. One notable example is Dazai, whom he saves from "drowning" during their first encounter, albeit with some inhibition initially. During his secret entrance exam where he was faced with a simulated bomb threat, he used his own body to cover the bomb and shield the other members, also people he had never met.

He has a strong sense of morality, which also directly stems from his upbringing. He believes his worth in life depends on his ability to protect others and has an aversion to the abuse of one's power and to preventable deaths.He even tries to help even his enemies at times and would often feel sympathy for most of them, as seen through his interactions with Kyōka, Lucy Maud Montgomery, Sigma, and even Fukuchi during his supposed death.