Kishou Arima (有馬 貴将, Arima Kishō) was a Special Class Ghoul Investigator famously known as the CCG's Reaper (CCGの死神, Shīshījī no Shinigami). He was a prominent figure within the organization and was widely regarded as a genius. In the prequel spin-off Tokyo Ghoul: Jack, he is featured alongside Taishi Fura as a teen.
He garnered an impressive list of achievements during his eighteen years as an investigator, from leading the prestigious S3 Squad to single-handedly turning the tides of large operations. His lethal battle prowess earned him many names, including the White Reaper (白い死神, Shiroi Shinigami), among others.
However, beneath the surface, Arima was sided with ghouls as the mysterious One-Eyed King (隻眼の王, Sekigan no Ō). Conspiring with Eto Yoshimura, he gained the ownership rights of Ken Kaneki after the Owl Suppression Operation and mentored him in preparation to bestow the title to him after his death.
Arima was a tall, well-built man with snow white hair and gray eyes. He always wore a pair of thin-framed glasses and a calm apathetic expression. He always dressed in a professional suit and tie, adding the pure white coat that acted as the S3 Squad uniform during operations.
During his youth, Arima had dark blue hair and was much shorter in height. While attending Seishin High School, he wore the standard school uniform. He carried a guitar case with him at all times to conceal his quinque, Yukimura 1/3, as opposed to the standard quinque case.
Arima was shown to have a very calm personality, he remained unperturbed and composed even when surrounded by several ghouls or facing the monstrous One-Eyed Owl. He was also an overly strict mentor, as seen when he reprimanded Hirako for being off on his attack by one decisecond. As a teenager, Arima exerted the same personality, and also noted his main hobby to be ghoul extermination. He had a very cold and calculating approach to exterminating ghouls as shown when he was about to finish off Renji Yomo, and Yoshimura appeared suddenly; instead of panicking or attacking he merely greeted the ghoul. Arima was shown to respect the dead as he reprimanded Itsuki Marude when he talked ill about Mado after his death.
Despite his stoic demeanor, he was capable of forming friendships, he often borrowed books from Haise Sasaki, and Akira Mado described his feelings towards Sasaki as "parental love." Arima was also the type of person who complimented his ghoul opponents, an example being when he did so when Kaneki damaged his quinque, IXA. Surprisingly while dying he reveals he despised himself for killing ghouls. He admits how happy he is to have done something good by imparting his mission to depose V and become a symbol of hope for ghouls.
Arima was hailed as a genius within the CCG, stemming from his affiliation with the organization since his teens. He was personally selected by CCG's chairman Tsuneyoshi Washuu to be promoted to a 3rd class investigator. Taking advantage of his youth, he took on assignments that regular investigators could not handle. One such assignment saw him working undercover as a transfer student in the 13th Ward, where he became the classmate of Taishi Fura. Sent to eliminate the ghoul Lantern, he rescued Taishi and the two formed a partnership to hunt the ghoul down. Their activities soon caught the attention of several ghouls in the ward, as two high school students killing ghouls was unheard of before.
The pair rescued Uruka Minami from Sumiharu Katou, a ghoul posing as a hairdresser and agreed to let her aid them in their investigations. Though Taishi believed Minami to be in love with Arima, in truth she was simply trying to manipulate them. At an abandoned house, Minami revealed herself to be Lantern and tried to kill Arima — who had already suspected her. Though he fatally wounded her, Taishi was forced to deliver the final blow in self-defense. Afterward, Arima left to take on his next assignment.
Due to his outstanding talent, he was promoted to Rank 2 in less than a year. During the rampage of the One-Eyed Owl, he took part in the defense of the 2nd ward — used numerous quinques to challenge and defeated a disguised Yoshimura in battle. From this battle, he obtained a kakuhou that would be used to create the SSS-rated quinque Owl.
At an unspecified point, he found and defeated Eto Yoshimura at her shrine hide-out. Rather than simply kill the infamous One-Eyed Owl, he questioned her about her motivations and learned of her desire to change the world. Interested in her ideals, Arima spared her life and allegedly began to conspire in secret with her.
In the passing years, he partnered with Take Hirako. The pair took part in the extermination of the Clowns in the 4th ward, coming into conflict with Uta's gang. There, he was confronted by the younger brother of Hikari Kirishima, Renji Yomo. Before he could deliver the finishing blow, Yoshimura interrupted and rescued the young ghoul from him.
Owl Suppression Operation
After being given the mission to ambush any fleeing ghouls and neutralize the One-Eyed Owl, Arima was stationed within the underground Route V14, where he encountered and single-handedly killed dozens of ghouls. Upon having his gaze fall on Ken Kaneki, he quickly approached him with the intention of completing his mission and, without warning, dealt an attack towards Kaneki that tore a large chunk out of his abdomen. Before Kaneki could recover and fight, Arima lunged his quinque IXA through the back of Kaneki's skull, which pierced his brain and destroyed his left eye. He easily dodged Kaneki's rapid kagune strikes and witnessed a sudden emotional outburst from Kaneki, during which Kaneki recited a Hakushū poem. Apparently moved by the poem, Arima made note of Kaneki's identity, then offhandedly mentioned that he could tell it was raining outside from the sound of water pouring in from above. He stated that his sense of time got dulled when he was underground.
Arima then brought out his other quinque, Narukami, and activated it. He declared that his objective was to ensure no ghouls would pass through Route V14, and released bolts of Rc projectiles towards Kaneki. After Kaneki dodged those attacks, Arima commanded his quinque to go into remote activation and continued to strike at Kaneki, keeping the manic ghoul at bay. He blocked a desperate attack from Kaneki's kagune using IXA's defensive barrier, but was surprised that Kaneki's blow managed to break the barrier, and so complimented his opponent. Arima went on to impale Kaneki through the abdomen with IXA, lifted him high into the air briefly before he threw him back to the ground. Arima stated that he had not expected Kaneki to damage his quinque and finished Kaneki off with a stab through the other eye and mentioned that he needed a new quinque. Arima noticed a bleeding scratch on his right cheek. Later on, he confronted the One-Eyed Owl alone and managed to sever its arm, forcing it to escape and mirrored his battle with the first Owl years ago. Later it was revealed that their battle was only a performance and in reality Arima let Eto escape with Yoshimura as a part of their plan.
Years later, Tatara recalled Arima dragging a half-dead Kaneki by the hair after the latter's defeat. Tatara bowed as he passed.
Post-Owl Suppression Operation
After the CCG imprisoned Kaneki in Cochlea, Arima visited Kaneki in order to observe him. During one such visit, Arima witnessed an emotional outburst by Kaneki, now called Prisoner #240. As Kaneki frantically begged to be let out to save his friends, Arima calmly told Kaneki that he had killed all of them. He inquired about the amnesiac Prisoner #240's state with the Warden Shinme Haisaki. Haisaki told him that Prisoner #240 was refusing food, was apparently tormented by nightmares that made him cry worse than a baby during the night, and picked at his eyes so much they were festering; thus, the Warden expected the prisoner to die soon due to starvation. Thereafter, Arima started to bring Prisoner #240 books to read, and Prisoner #240's health improved substantially.
Alongside Yoshitoki Washuu, he discussed the results of the operation with Chairman Tsuneyoshi Washuu. The chairman turned to Arima and asked him what he would do about the name as the 'ownership rights' were his. Arima replied that he would entrust this to 'him'.
During another visit, Arima told Prisoner #240 that he would need a name, as it was planned for Prisoner #240 to be appointed an investigator during his rehabilitation. He asked Prisoner #240 to pick his new name, and by using Prisoner #240's two favorite kanji from the words "coffee" and "world", they formed the name 'Haise'.
Some time after the Owl Suppression Operation, Arima along with Akira Mado were in charge of supervising Haise Sasaki and his Quinx members. Following the failed operation to capture Torso and Serpent, Arima summoned Haise to an S3 meeting. He did a minor spar with Haise, subsequently returned the book he borrowed from Haise to him. When Sasaki apologized for using his kagune to fight Serpent, Arima dismissed this apology, and listened attentively as Haise compared him, Akira and the rest of the Quinx Squad to a somewhat dysfunctional family.
After the second operation during the Auction Raid, Arima arrived at the auction location near the end of the raid with his Squad and members of S3 Squad. He, along with the rest of his squad confronted Hinami Fueguchi, who after her fight with Takizawa, was in no fit state to put up a fight. He approached her and was stopped by Haise Sasaki, which made him tighten the grip on his quinque. Haise asked him for ownership rights over Hinami, which he granted before ordering his squad to call for the medical team to deal with Haise's wounds.
A month had passed since the Auction mopping-up operation and he attended a Christmas party at The Chateau, arriving with Akira. He enjoyed himself in the company of everyone and talked about the bizarre stories that surrounded him, like the time he fought a ghoul with an umbrella, fell asleep during a fight, and how ghouls were so afraid of him that they fainted on the spot and were taken straight to prison. These stories turned out to be true. He received a tie-pin with a decorative horse as a present from Sasaki.
Koori was visited by Arima, who had heard of his operation commander position from Marude earlier, and expressed ease as his former superior was the only one he could feel relaxed around after being promoted to Special Class. Koori attempted to tell Arima something, but his former superior was then called on by a fellow employee and left before anything else could be said.
A vision of him later appeared before Sasaki in what appeared to be a training session, Arima acted cold towards him and told Sasaki to kill like him. This vision of Arima then held IXA to Sasaki's eye and asked if he wanted to die again.
Arima approached Furuta, to deliver a message that V called for them in regards to Ken Kaneki. The two proceeded to report in at one of said organization's locations about the whereabouts of Eto and the likelihood of her being the "King". Kaiko ordered Arima to deal with a problem involving Rize.
He later confronted Shachi and fired a bolt of condensed Rc cells at him with Narukami. Shachi dodged as Arima declared that he will capture and exterminate him. During the fight Shachi noticed a strange pause in Arima's strikes and concluded that he had a "blind spot". After the other squad members were defeated he was left alone to face Shachi, who tried to take advantage of his weakness and struck from his blind spot. However, Arima dodged the attack and countered by stabbing Shachi's left eye, pierced his throat with Narukami, and sent a wave of condensed Rc cells coursing through his body. Gravely wounded, Shachi slumped to the floor, and admitted that despite Arima being his enemy and having those eyes, his fighting skills were magnificent.
Third Cochlea Raid
During the Rushima Invasion, he and his squad were assigned alongside Mougan Tanakamaru's and Kiyoko Aura's squads to protect Cochlea while the main invasion team attacked the Rushima. Arima patrolled the facility and headed for the main building, leaving a section of the prison in Sasaki's care.
Afterwards, as the ambush on Cochlea began, Arima fired a bolt of condensed Rc cells at Ayato Kirishima, who was saved by one of Banjou's group members. As their battle began, Ayato fired bolts from his kagune at Arima at close range, but Arima blocked them easily with one hand. Ayato tried to strike from behind, but his kagune was blocked by Arima, who countered with a strike that narrowly missed him. Arima activated IXA and shot another bolt at Ayato which grazed his mask and destroyed it. He quickly followed up with several strikes to Ayato's legs. Having rendered Ayato immobile, Arima prepared to deliver the final blow. However, his quinque was blocked by Renji Yomo. Arima was then flanked from behind as Touka Kirishima shot at him with her kagune. Arima quickly blocked the shards with IXA's shield, and narrowly dodged a punch from Renji. He countered with Narukami but the blow was similarly dodged by Renji. When the emergency doors opened, the three ghouls escaped, leaving Arima watching them.
Arima intercepted the three again when they tried to access a door to the containment cell tower. He split the three up by firing a bolt at them. He then focused his attention on Renji, firing repeatedly at him and eventually grazed his arm. Having distracted Renji, Arima struck at him with Narukami. Touka attempted to block the blow but Renji pushed her away, taking the blow at his neck.
As Yomo fell to the ground severely wounded, Ayato and Touka attempted to attack Arima, the latter easily repelled both of them. Yomo revealed his kagune and charged a lightning bolt, fired it towards the investigator who blocked the attack with Narukami, damaging the quinque in the process. As Arima fired one last Rc projectile at Yomo to finish him off, Sasaki suddenly intervened and blocked the projectile with his kagune.
Sasaki was immediately attacked by Arima, who threw Narukami away and now wielded IXA. Sasaki revealed a large kagune after Ayato, Touka, and Yomo escaped. He repeatedly attacked Arima, but the investigator parried all of his attacks and pierced him in the abdomen, which Sasaki quickly recovered from. They both exchanged numerous blows with each other. As Sasaki tried to attack Arima in his blind spot, Arima swiftly countered the attack and sliced both of Sasaki's legs off. He approached the wounded Sasaki and pointed IXA at his head. While the former tried to reattach his legs, Arima ripped them off again. He stabbed Sasaki multiple times, goading him to fight seriously. After finally recovering, Sasaki launched a sudden, powerful attack towards Arima, which the investigator blocked with IXA, shattering the weapon into pieces. Cornered, Arima called out to a mysterious figure to lend him a new quinque. Displaying this new weapon, Owl, Arima revealed the quinque was made from the kakuhou of the Non-Killing Owl that he battled when he was 19, and it was his first time using it.
Sasaki jumped and attacked Arima, who nonchalantly evaded the attack and countered with a barrage of projectiles. Sasaki blocked the projectiles and pierced through Arima's coat with his kagune. Arima quickly removed his coat and charged forward to confront Sasaki. As Arima and Sasaki clashed head to head, Sasaki wrapped his arm around Owl, restraining Arima from attacking. Arima quickly shook Sasaki's binding by releasing Owl's blade, which he then remotely activated so that it materialized below Sasaki and impaled him. With Sasaki stunned and injured, Arima quickly recalled Owl's blade and severed both of Sasaki's arms. Arima proceeded to slash Sasaki numerous times midair, preventing him from healing any of his injuries, until Sasaki collapsed onto the field of flowers. Miraculously, Sasaki recovered regaining his identity back as Kaneki Ken, and got back up as his kagune began to replace his limbs. Before resuming the battle, Kaneki smiled confidently at Arima, who responded with a faint smile of his own. Armor then emerged from Kaneki's kagune and slowly covered his entire body apart from his head, and their clash continued. 
Kaneki began to attack Arima from afar with his kagune, which Arima countered by slicing the tentacles off. Realizing that simple frontal attacks would not affect Arima in any way, Kaneki burrowed his kagune underground, shaping it into a net. Arima leaped through the net in order to reach Kaneki's position, only to be surrounded by numerous tentacles on all sides, in response, he slashed and destroyed all the kagune around him. Afterwards, he noticed a sound behind him and immediately attacked it with Owl, only to discover that he had merely slashed one of Kaneki's tentacles. Taking advantage of this, Kaneki struck at Arima from behind. The investigator managed to block Kaneki's attack in time, but Owl was destroyed by the force of the blow.
Though Kaneki declared the battle over, Arima charged him and stated the battle will not end until one of them died. He continued to attack with the broken quinque, slashing apart tentacles until he closed the distance between them and stabbed Kaneki through his abdomen. However, Kaneki pleaded with him to accept his defeat and voiced his belief that continuing was meaningless. Arima stepped back, lowered his broken quinque and asked whether Kaneki has no intention of killing him. After Kaneki's response, he turned his gaze upwards, mused that in his eighteen years as an Investigator, he had never faced an opponent he could not defeat. Once more, he asked Kaneki whether he will really not finish him off. Kaneki confirmed his decision once more, and after he stated his understanding, Arima slashed his own throat with Owl.
Mortally wounded, Arima collapsed with blood pouring from his throat and mouth. As Kaneki held him, he used the last of his strength to confess his many secrets. He revealed himself to be a Half-human, a ghoul-human hybrid born without a kagune, bred by the Sunlit Garden. Because of his hybrid nature, he had developed glaucoma as a result of an accelerated aging progress and would soon die from old age. He revealed to Kaneki that the Washuu Clan were ghouls, and entrusted him with his final wish — Kaneki to take credit for his death. He promised that Kaneki would understand soon enough, and admitted that he always hated his own existence as someone that could only kill, taking the lives of others while never giving anything to the world in return. With his dying breath, Arima praised Kaneki as something he could leave behind and lifted his hand to touch his face, before he succumbed to his wounds.
According to Akira, Arima possessed “parental love” for Sasaki, as they usually lent each other books and Arima even checked on Sasaki regularly. Even though Haise claimed he had a “make-believe” family, Arima was like his father figure. Arima often sparred with Haise as a means of training, and gave him advice when he was in need of help. In his final face-off with Sasaki, Arima claimed that he could have killed the latter 645 times but decided to spare him, and provoked him in order to get Sasaki to fight him seriously. During his last moments, he revealed the secrets of the Sunlit Garden, his origins and his past to Kaneki, and said he was glad for leaving something behind him. Eto and Arima cooperated in order to find and nurture somebody to become the One-Eyed King, the individual that would become the hope for ghouls, who later turned out to be Kaneki himself.
The two met as teenagers, when Arima defeated her in battle. However, her desire to change the world caught his interest and the two began to conspire together against his superiors. The extent of Arima's involvement in her plots remains unknown, though he aided her in keeping his superiors misinformed with the belief that the One-Eyed Owl and the One-Eyed King were the same. He also allowed Eto to pass through the CCG's containment net during the Owl Suppression Operation, and then let her escape with Yoshimura after briefly fighting her.
Hirako was Arima's former partner. Arima both trained and mentored him as his subordinate. As Arima always looked down to him as a rookie, and often scolded Hirako for minor imperfections, it seemed to be implied that Hirako had an inner hatred for him as evidenced by his immediate strike when Uta wore his Arima mask. This implication ultimately proved to be false, however – Arima trusted him enough to not only reveal his secrets, but to leave Hirako to carry out his final wish. Acting under Arima's orders, Hirako betrayed the CCG.
Arima and Taishi knew each other for over twelve years. They attended the same high school for a short while, and were even in the same class. As teenagers, Taishi and Arima embarked on many ghoul investigations, where they were shown to look out for each others' well-being. However, because their personalities were so different, they often had trivial quarrels, where Fura would accuse Arima of not "living a normal life."
Arima was Koori's former mentor, having been partnered together in the past. Koori seemed to share a rather friendly relationship with Arima, being one of the few that Arima had been shown to smile to. Koori also noted that after being promoted to Special Class, he could not seem to be at ease with anyone other than his former superior. He respected his former mentor greatly, as he thought of him as a genius.
A former member of Arima's squad and his half-sister. They were both raised in the Sunlit Garden. Details about their past history is shrouded in mystery. Apparently, she thought of him as "super strong."
Amon admires and respects Arima, viewing him as a role model of a ghoul investigator. Arima commended Amon for his promotion to a senior investigator and efforts during the 11th Ward Battle.
The two have worked together for years and admired each other as fine investigators. Together they supervised the Quinx project and Sasaki acting as guidance figures. Akira considers him to be CCG's greatest strength.
According to Akira, her father once mentored Arima by teaching the latter everything he knew about quinques. While the two don't seem to interact with each other anymore, Arima still respected Mado enough to reprimand Marude when he spoke ill of him.
Since becoming an investigator, he and Arima shared a positive, professional relationship. They often participated in Whack-a-Mole operations together.
Despite being the older investigator, Tanakamaru admires Arima's fighting skill. During the battle with the One-Eyed Owl, Tanakamaru praised Arima for attacking while evading like a swift wind, even shedding a tear.
Urie looked up to Arima and was thrilled when he heard him praising his talent and giving the approval for his frame release surgery. This increased Urie's determination to become better and assured himself that he would not lose control like Sasaki.
Like many of his fellow ghoul investigators, Itou respected and admired Arima, viewing him as a symbol of strength. During Sasaki's Christmas party, Itou claimed that he heard a rumor from Hirako about Arima defeating a ghoul with an umbrella instead of IXA, and believed in it. Itou also claims that Arima was the one investigator all the ghoul investigators looked up to.
The personal relationship between them is unclear, however, they were half-brothers and were both involved with V. Arima sought Furuta out to inform him that V was calling about Kaneki. Despite this, neither of them actually cared about each other, as after Arima's demise, Furuta showed a lack of care or grief for his half brother and Arima on the other hand was the secret One-Eyed King and worked with Aogiri Tree to destroy V, clearly showing he feels nothing for Furuta.
Arima is one of many illegitimate children of Tsuneyoshi Washuu. He was the only one of the children who interacted with his father. Tsuneyoshi held Arima and his abilities in high regard, and in turn, Arima addressed him formally and was shown to have a level of professional respect for him. However, Arima was the secret One-Eyed King and worked with Aogiri Tree to destroy V and despised his own existence for solely killing ghouls as well as his nature as a soon-to die half-human, strongly indicating he hated his father since he was responsible for both of this things.
Souzu is a member of Arima's squad, serving under him. They were loyal towards Arima and respected him.
The two were members of the Arima branch family, but they weren't close relatives. Nevertheless, Yusa respected and admired Kishou, as shown when he cried and mourned the death of his squad leader.
Shio is a member of Arima's squad, serving under him. He cried and mourned over Arima's death, showing that he respected and cared greatly for him.
The relationship between these two is quite unclear, other than what was briefly shown in Tatara's flashback moments prior to his death. Tatara seems to be aware of the goal between him and Eto to create a Ghoul who could defeat and kill him. He had a deep respect for Arima, as he refers to him as "King."
Noro was known to be a direct subordinate of Arima.
As Arima killed his sister whilst he was absent on said encounter and since that incident, Yomo harbors deep hatred towards the ghoul investigator. Arima himself treated him like any other Ghoul he would fight, ruthlessly attempting to dispatch him and never speaking anything to him, along with the fact he was likely not even aware the reasons of Yomo's anger. Even after being informed of Arima's true intentions for ghouls and possibly his half-human heritage, Yomo's hatred for the late ghoul investigator did not falter. Remarking that if the man who took his sister's life is still alive and standing before him, Yomo wouldn't hesitate to kill Arima on the spot.
Arima and Shachi engaged each other in a brief battle, in which Shachi was elated to face the CCG's Reaper in battle. When Shachi was defeated, he praised Arima for fighting magnificently well before collapsing.
Powers and Abilities
Half-Human Physiology: Being a failed half-ghoul, Arima was granted increased physical abilities at the cost of a shortened life span.
- Superhuman Agility: Arima was capable of dodging Kaneki's enormously destructive and rapid attacks, suffering a small cheek wound after the blow, after slaughtering a large amount of fleeing ghouls underground. During his life, he repelled both Yoshimura and Eto. His reflexes are sufficient enough to deflect a barrage of ukaku shards shot by Ayato Kirishima, block Touka's projectiles and parry Yomo's attacks at close-range. He was also able to easily outmaneuver Shachi's attacks, and counter the martial artist's movements. His speed is fast enough that he is able to keep up with Kaneki at his Half kakuja state at Cochlea arc and is able to dodge all of Kaneki's attacks.
- Keen Intellect: Arima is shown to be very deductive throughout the series. As a teenager, he easily memorized all the formulas in the math textbook and managed to deduce Uruka Minami as a ghoul with a single piece of evidence. As an adult, Arima secretly uncovered the identity of the "One-Eyed Owl" as Eto Yoshimura and deduced the identity of Ken Kaneki when the two first battle at the end of the original series.
Master Swordsman: Having extraordinary skill with his quinque, Arima could quickly block projectiles and easily slice through a ghoul's kakuja.
- Yukimura 1/3: A koukaku-type quinque that takes the form of a sword consisting of a long, thin blade without a guard. This quinque was used during Arima's early days as an investigator.
- IXA: A koukaku-type quinque that takes the form of a lance attached to a gun-sword handle with a spiked pommel. It is able to change form into a shield that is capable of blocking potent attacks coming towards Arima. It is also capable of changing into a secondary offensive form that changes the shape of the quinque into several tentacles which can home and pierce any enemy of Arima's choosing.
- Narukami: An ukaku-type quinque that takes the form of four satellite panels attached to a rapier handle. The quinque can shoot condensed Rc cells like lightning that can home towards a target of Arima's choosing. It also has the ability to combine the panels into a single rapier blade sharp enough to slice through the One-Eyed Owl.
- Owl: Ripped out of the One-eyed Owl (later revealed to be the Non-Killing Owl Yoshimura) thirteen years ago, this quinque is an SSS-rated ukaku-type that takes the form of an elongated large blade with a long hilt. Being an ukaku quinque, Owl can shoot out concentrated Rc cell projectiles of various sizes. Furthermore, Owl's blade can be released and materialized remotely to launch an attack on a target from an unexpected location.
- He was the one of two people (the other being Juuzou Suzuya) to be promoted to a 2nd Class Investigator in less than a year.
- In the first character popularity poll, Arima was ranked fifteenth. In the latest, he came in as seventh.
- He shared the same birthday with Ken Kaneki.
- Arima held the highest kill count and number of conferred decorations within the CCG.
- While he originally had dark blue hair, his hair gradually became white over the course of his twenties. This was presumably because of his accelerated aging process.
- Arima had been associated with the number "13." It referenced the tarot card Death (XIII).
- His relationship with Sasaki referenced Franz Kafka's short story, A Crossbreed. The narrator is the owner of an unusual creature that is half-kitten and half-lamb.
- In :re Chapter 31.5, the Quinx Squad and their guests discussed some of the myths surrounding Arima, namely that he slept between missions and that he once defeated a ghoul with an umbrella. Surprisingly, Arima confirmed both of these to be true. He killed the ghoul with an umbrella as his quinque ‘IXA’ was being repaired and he slept between missions to keep himself alert.
- He has the same English dub voice actors as Shota Aizawa from My Hero Academia.
- In Tokyo Ghoul Trump, he is featured as a "Black Joker."
- He likes to challenge his subordinates in sparring sessions in the meeting room as shown in the omake of :re Volume 1.
- When a fan asked Ishida how to draw Arima, Ishida responded that he kept "sadistic & massive" in his mind.
- Arima and Sasaki's family names are both present in the list of Japan's Kōke families during the Tokugawa Shogunate. The Arima clan was first on the list, while last on the list was the Rokkaku clan of whom many kept their family name from their origins from the Sasaki clan.
- Ishida has stated that Arima's theme was "Protagonist: In The Future."
- To Minami: "Events that happen in this world, are a continuous series of trifling things, and within those myriad pieces of puzzles, there is always a fragment that leads to the truth."
- To Ken Kaneki: "...Oh, I see... You're... It's raining. I don't know what the weather outside is when I'm below the surface. My sense of time also gets dull. But I know if it's raining outside from the sound of water... It'll be over soon. We're in V14. No 'ghoul' can pass through here. You can't go any further than 14."
- To Ken Kaneki: "645 times. 645 times I could have fatally wounded you. 645. 645 times I decided not to. It would take me two seconds to kill you. Your eyes are the eyes of a dead man. The dead cannot stop me."
- To Ken Kaneki: "Defeat, huh... Eighteen years. Eighteen years have I been an investigator. And yet this is the first time I am faced with an opponent against whom I have no course of action."
- To Ken Kaneki: "I... I've... always... hated it. I hated myself, who only ever stole from others... I was finally... able to leave something..."