Atsushi Nakajima/Relationships

Orphanage Director
Atsushi carries hatred and deep fear toward the Headmaster of his orphanage, who acted as his caretaker. His negative feelings are due to the Headmaster torturing and abusing him verbally, physically, and emotionally throughout his entire life, up until he was thrown out of the orphanage.

Upon the Headmaster's death, Atsushi goes through emotional turmoil and confusion. Dazai helps him realize that he became someone who understands suffering, resists violence, and saves people. However, Dazai also tells him the treatment he went through was barbaric, and that Atsushi obviously is under no obligation to forgive him. When confused about how he should feel, Dazai tells him that usually one cries when losing a father. To this, Atsushi breaks down and cries in both bereavement and relief.

The abuse that Atsushi suffered under the Orphanage Director's hands still affects him in his day to day life, which was severe enough to give Atsushi daily nightmares and flashbacks, and cause him to hear regular phantoms of his voice as the source of his internal self doubt. He carries so much fear that seeing a mere image of his Headmaster is enough to cause him to panic, and he remarks that the fear he felt in that moment was more intense than even his most tense battles.

Osamu Dazai
Dazai is the first member of the agency Atsushi meets, encountering him when rescuing him from drowning in a river. Dazai quickly assumes responsibility for him, taking him to eat and happily conversing with him. He bribes Atsushi to become bait for the tiger since Atsushi admits that it had been "following" him. Upon discovering that Atsushi himself is the tiger and an ability user, Dazai recommends him to the agency and even walks with him to his entrance exam, under the guise of taking him to a job interview.

Once in the agency, Dazai takes over as his supervisor. Throughout the events, he mentors and advises him, sometimes in the form of teasing or playfully taking advantage of him, such as asking Atsushi to write a report for him. Atsushi remains trusting, albeit bemused at Dazai's constant fluctuations in demeanor and priorities.

They form a closer relationship between them; Dazai often talks Atsushi through his several breakdowns, showing concern for his wellbeing in his eccentric way. In one notable and slightly more harsh instance, when Atsushi panics after harming Naomi and Haruno under Q's ability, Dazai slaps him and sternly tells him that pitying himself will make life an endless nightmare, ultimately snapping him out of a panic attack.

Doppo Kunikida
Kunikida is skeptical of Atsushi upon his arrival, shown when he scolds Dazai for spending his money on him and his proposition for Atsushi to join the Agency. Their ideals also clash a couple of times when Kunikida discourages him from trying to save Kyōka, telling him that he can't save everyone (most likely based on past experiences rather than strict ideals.)

As events progress, Kunikida and Atsushi have more of a mentor/mentee relationship, the former shown training him in the martial arts he learned from Fukuzawa and giving him advice.

Ranpo Edogawa
Being a new Agency member, Atsushi often wonders about Ranpo's words and actions. He is surprised to witness Ranpo's lack of what seems to be common knowledge, such as how to ride a train- he doesn't know how to buy a ticket or which platform to go into.

Atsushi's respect grows for Ranpo as he learns more about him, though he remains confused about the man. However, they are on friendly terms, Atsushi going so far as to letting Ranpo climb on his back for a ride.

Yukichi Fukuzawa
Like most other members, Atsushi has a healthy amount of respect towards Fukuzawa. He is slightly intimated by the severe man but still obeys him.

Akiko Yosano
Atsushi respects Yosano a lot, despite being afraid of her treatment. He doesn't seem to mind carrying her bags and boxes. He admires her for her strong will and attitude.

Kenji Miyazawa
Atsushi is partnered with Kenji when they investigated a car explosion incident. Though Atsushi thinks that Kenji's methods of investigating were questionable, he later then dismisses it and follows his lead. Due to naivety and how simplistic Atsushi is, he ends up finding Kenji's methods to be standard, until the pair get surrounded by a group of dangerous criminals, and Atsushi realizes that Kenji's methods work best for him alone due to his personality and ability. As Kunikida states, they are the best and worst team together.

Kyōka Izumi
Atsushi first encounters Kyōka when he assisted Yosano in shopping. He later founds out Kyōka has killed 35 people and wants to stop killing others, he then saves her from the bomb explosion. As someone who understands what she has gone through, Atsushi deeply cares about Kyōka as to accompanying her when they explored Yokohama. He also tries to protect when someone tries to hurt her. Despite caring for Kyoka, Atsushi has underestimated and has been naive about the true nature of her darkness and her ability to cause harm to others. This was evident when he refused to believe Koyo's statement that Kyoka would kill a mass number of people to preserve herself and that she had a natural talent in slaughter. This would be proven true when Kyoko attacked and nearly killed a police officer who tried to apprehend her. This would convince Atsushi that Kyoka's true nature was indeed in darkness and killing. Despite this fact, he has fought to give her a chance as he believe she was capable of change and overcoming her weaknesses.

Jun'ichirō Tanizaki
Atsushi first meets Tanizaki during his entrance exam to join the Armed Detective Agency. After Atsushi has been accepted into the Agency, Tanizaki apologizes for being mean to him. For Atsushi's first job, he is paired with Tanizaki and Naomi to investigate supposed smugglers in the area.

In later events, Atsushi is paired with Tanizaki once again by Ranpo to investigate the death of his orphanage director. Upset from seeing his orphanage directors face, Junichiro brings Atsushi coffee and attempts to console him, thinking Atsushi is sad from the death.

Though Atsushi and Tanizaki are of the same age, Atsushi calls him Tanizaki-san. This could possibly be due to Atsushi's feelings of inadequacy.

Ryunosuke Akutagawa
"It's true that I'm foolish and worthless. But it sure beats being you - a murderer who just wants to bandy his power around! Am I wrong? You've got the power and status but you still fight 'cos you want to be feared! That's far more worthless in my book."

- Atsushi to Akutagawa

Atsushi first met Akutagawa in a dark alley on a mission with Tanizaki and Naomi in which he was tricked by Higuchi who was on a mission to capture him. After his incident, he became to fear Akutagawa as a person who could kill him and would cower in fear about the though of him, but also developed a dislike and hatred of him. Later when he is captured by him and trapped on a boat, he is faced with an enraged Akutagawa who has come to hate him after he finds out Atushi is Dazai's current subordinate and is favored by him while he ws ridiculed by Dazai moments earlier. Thought initially fearful of him, when he saw how Akutagawa looked down on Kyoka and tried to kill her, he challenged him to a battle and demanded to know why he couldn't tell Kyoka anything better than that she was worthless if she coudln't kill. Enraged and full of bitterness and wishing to protect Kyoka, Atsushi defeats Akutagawa and leaves him in the ocean for dead.

Despite defeating Akutagawa and nearly killing him, Akutagawa would continue to live in Atsushi's mind similarly to how the Headmaster would speak to him through hallucinations. During their second meeting, Atsushi would project his hatred towards him and accuse Akutagawa for only being a serial killer who only wants people to fear him only to be strongly berated by Akutagawa that he is wrong and that he considered him disgusting for wallowing in self pity despite having everything including a wonderous Ability, friends who care for him, and praise from Dazai just by pure luck and not counting his blessings. It's from this encounter that Akutagawa gained more interest to know Atsushi more overall despite his scathing hatred and disgust for him, while Atsushi considered Akutagawa to be much stronger than him and worthy of Dazai's acknowledgment.

Over the course of their relationship, Atsushi has had a strong dislike and hatred for Akutagawa overall due to disagreeing for his belief systems about who and what is considered strong and considers his view on himself being weak as absolutely preposterous. His hatred for Akutagawa is similar if not parallel to his hatred for his Headmaster, which caused him to at times have unjustified hatred for Akutagawa in which he would dehumanize him as a monster who can only kill and hypocritically strongly reject his right to live, despite Akutagawa showing moments of compassion and proving him otherwise. These feelings only became stronger after the passing of his Headmaster in which he believe the only way to get revenge against him was to defeat Akutagawa and erase the Headmaster from his mind. Ironically, this mindset has negatively impacted the partnership between him and Akutagawa due to Atsushi having no trust in Akutagawa due to not having any desire to know and understand him and only rejecting him as a person.