Atsushi Nakajima

Atsushi is a member of the Armed Detective Agency who possesses the ability Beast Beneath the Moonlight. 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. Before joining the Agency, he wears rags issued by the orphanage, and after he joins the Armed Detective Agency, they issue him a white button-up with the sleeves pushed to his elbows from Doppo Kunikida, a loose black tie from Akiko Yosano, black pants from Yukichi Fukuzawa, black fingerless gloves from Ranpo Edogawa, suspenders from Kenji Miyazawa, and a long black belt from Osamu Dazai. When he transforms into a partial tiger, his eyes become tiger-eye-like, and he develops fangs. If more drastic, his limbs turn into into a tiger's, and his tail emerges. When he finally develops considerable control over his ability, he can transform fully into a white tiger with black stripes and retains the tiger's gold eyes. 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. He also tends to react strongly and believe things at face value, trusting others' judgment above his own and even abandoning his own instincts. For example, when learning of the ¥7 billion bounty on his head, he became convinced that he was putting the Agency at risk. He felt intense guilt and decided to leave, believing it will keep the Agency from being targeted. 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. However, Atsushi still experiences paralyzing fear of fighting alone and often needs a companion to aid him in battle or at times save him in order to feel confidence.

Atsushi grew up in an orphanage, where he suffered from severe abuse – both verbal and physical – from his caretakers, as well as social isolation from the other children. This history of mistreatment has evidently taken a huge toll on Atsushi's self-worth as an adult and has caused him to constantly question the value and usefulness of his life. According to the orphanage director, Atsushi's parents dumped him. The director becomes the foundation of Atsushi's warped self-worth. The abuse, presumably severe especially because of the tiger rampaging at night, led the director to occasionally chain Atsushi in a cell with little to no food for at least three days. Atsushi was also forcibly injected with what he thought might be poison (which Atsushi later thought in his adulthood might be nutrients). Moreover, at one point, the director forced Atsushi to hammer a nail into his own foot as a way of teaching him how to "endure pain". When he was unable to, the director himself hammered Atsushi's foot, afterwards instructing him to reflect on his own. The director emphasized Atsushi's hatred towards him, seemingly even encouraging it. Alongside the director and other caretakers' abuse, Atsushi suffered at the hands of the other orphans. Oftentimes, the other orphans threw Atsushi under the bus when they got in trouble, as the orphanage ran on some sort of point system that affected if and when they were fed. Once he hits 18 years old, Atsushi was kicked out of the orphanage under the pretense that they had a lack of funding and had to downsize. Though he was unaware of it at the time, he was actually transforming into a white tiger under the moonlight due to his ability and causing chaos, including destroying crop fields and storehouses.

Beast Beneath the Moonlight is his ability, and Atsushi has the ability to transform into a white tiger. At first, he doesn't seem to have much control over the transformation, likely due to the fact, or caused by, his unawareness of his state as an Ability user.

After becoming an official member of the Agency and under the influence of All Men Are Equal, he gains more control over his transformations