Atsushi Nakajima/Relationships

Orphanage Director
Atsushi carries hatred and deep fear toward the Headmaster of his orphanage, due to him torturing and abusing him verbally, physically, and emotionally. After the orphanage director's death, Atsushi still cannot forgive him no matter what he does. Though to which Dazai says that living through the hell he experienced with the director shaped him to the way he is now. He became someone who understands suffering, resisted violence and evil and saved many weak people. After realizing this, Atsushi grievingly cries.

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.

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 Kyoka, 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 Yukichi Fukuzawa and giving him advice.

Ranpo Edogawa
Being new to the agency Atsushi often wonders about Ranpo's words and actions. He was even surprised that Ranpo does not know anything including how to buy a ticket or which platform to go into and concludes that he cannot o anything without his ability. However, this thought of Atsushi was changed when he founds out that Ranpo does not have the ability and is not actually gifted. He then realizes why everyone in the agency trusts Ranpo so much. He also respects and obeys Ranpo as to letting him ride 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 Kyoka when he assisted Yosano in shopping. He later founds out Kyoka 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 Kyoka as to accompanying her when they explored Yokohama. He also tries to protect when someone tries to hurt her.

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 Edogawa 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.