Aoba Kuronuma (黒沼 青葉, Kuronuma Aoba) is a first-year student at Raira Academy and Mikado's junior. He is the original founder of the Blue Squares. Aoba has a bright personality and is always seen smiling, but he has a darker side that is highly manipulative and cunning. He is described as being akin to "a younger version of Izaya Orihara." Aoba appears in the second season of the anime and is involved in the events of Durarara!! SH.
Physically speaking, Aoba is an average-looking teenager with dark blue hair and brown eyes. In the light novel, his features are usually described as girlish and child-like, and he is short enough to be mistaken for an elementary or middle school student. He wears the standard Raira uniform at school and usually wears a light blue hoodie and a t-shirt as casual clothes. He has an average physical frame but is surprisingly decent in a fight. His true strength lies in his mental capabilities as he is a thorough planner and an effective manipulator.
Aoba initially appears very cheerful, outgoing, and friendly. Mikado even states that Aoba even reminded him of Masaomi in a way upon first meeting him. However, it is quickly revealed that Aoba is actually very devious, manipulative, and ambitious. He mostly keeps people at an arms length with very few exceptions, such as the Orihara twins, especially Kururi. Those who know his true personality consider him to be a younger version of Izaya, which is true to a certain extent. Like the aforementioned info broker, he is very cunning and enjoys toying with others, but unlike Izaya, who loves humanity, Aoba despises humanity with all his heart. He views most people as a means to an end and even uses his own brother as a figurehead leader for his gang when things went sour. Albeit, their relationship was very far from ideal, as Ran thoroughly abused Aoba for years before the fact. The fact that he was still willing to set his brother up for prison implies a high degree of ruthlessness on Aoba's part.
Despite these negative feelings towards humans, Aoba also fears isolation. After seeing the similarities between himself and Izaya, and seeing how isolated Izaya had become from almost everyone who knew him, Aoba begins to take a conscious effort to connect with others more often, mostly with the Orihara twins, whom he has mixed feelings toward. While he still remains distant from others, Aoba slowly begins to open up more around his friends and his outlook on life slowly starts to change.
Aoba's life was fairly normal during his early years although he was no stranger to family drama. Aoba's older brother, Ran Izumii, would occasionally abuse and bully him due to jealousy over their parents treating Aoba better than Ran. Aoba normally took these beating without too much complaint but would periodically get back at Ran in the form of pranks. In one instance, when Ran had overdone it, Aoba set his brother's room on fire and blamed it on his smoking habit. Aoba started Blue Squares when he was in middle school but handed leadership over to Ran in order to use him as a scapegoat should things go south. Ran proved to be a poor choice as he frequently made decisions without Aoba's permission and even initiated a gang war with the Yellow Scarves. The resulting conflict with the police caused Ran to get arrested and nearly destroyed the Blue Squares, much to Aoba's annoyance. He then received an invitation to join the dollars and accepted, seeing it as an opportunity to rebuild his gang.
At some point during middle school, Aoba walked downstairs to find Izaya Orihara sipping tea and chatting with his mother. Izaya apparently claimed to be Aoba's cram school tutor and had come to give his School ID back to him. Aoba knew that this was a blatant lie as he had his ID on him at that time but he didn't want to cause a commotion in his house. He and Izaya stepped out and discussed why Izaya had come. Izaya is surprised that Aoba was able to obtain his personal information through the Dollars network while Aoba is surprised that Izaya tracked him down so quickly. Aoba and Izaya immediately begin to dislike each other mostly due to the fact that their personalities are too similar.
Mika Harima Arc
While unseen, he later reveals that he was present at the mass Dollars meeting.
After the opening ceremony for the new year ends, Aoba approaches Mikado and Anri in the hallway. Aoba easily overwhelms the two of them with his cheerful personality (which vaguely reminds them of Masaomi) and asks if they can give him a tour of Ikebukuro since he doesn't know the area very well. Not really giving them the option to say no, the three of them set a date for the next day. Later on, during class, Aoba is placed in the same room as Kururi Orihara. He sees Kururi's desk vandalized by several bullies and realizes that the only reason they were bullying Kururi was because Mairu was actually able to fight back while Kururi wasn't. Aoba simply ignored it until the teacher started asking who was responsible. Aoba ratted out the bullies without a second thought, much to their surprise. He didn't do it out of a sense of right and wrong but simply because someone asked him a question that he had the correct answer to. The bullies later confronted him about it and asked why he betrayed them. Aoba replied that he was never on their side to begin with and notices the bag of one of the girls on fire. After the bullies ran away, Mairu and Kururi show up and comment on how fast they can go. As Aoba realizes that it was probably Kururi who lit the bag on fire, he is kissed on the lips by Kururi as thanks for helping her. Before this information can register, Mairu also kisses him in order to get an indirect kiss from Kururi. As the twins leave, Mairu warns Aoba that, despite her appearance, Kururi is actually very aggressive. Aoba is left speechless.
The next day, when Aoba, Anri, and Mikado meet, they are immediately approached by several remnants of the Yellow Scarves looking for revenge. They are chased off by Kyouhei and his group, but the trio are also shoved into Saburo's van in the process. Aoba sees the twins also in the back and is visibly surprised. After Toramaru catches up with them, the nine occupants begin a frantic chase through the Ikebukuro streets, eventually being joined by Celty. Celty tells the others to run while she holds off the motorcycle gang Toramaru. Kyouhei drops off Aoba and the other high schoolers near a police station while he, Saburo, Walker, and Erika go back to help Celty. Aoba and the twins head back to the overpass out of curiosity and watch with confusion as Egor and Ruri dispatch Toramaru. Later, he attends the hotpot party at Celty's apartment.
Several weeks after the incident with Toramaru, Aoba invites Mikado and Anri on another tour through the streets of Ikebukuro since their last one was interrupted so suddenly. Mikado, having just received the warning from "Masaomi," tries to get out of it, saying he had errands to run. Aoba accepts it without any objections but also starts to (not so) subtly flirt with with Anri, even going so far as to switch from using "Sonohara-senpai" to "Anri-chan" without any warning. Although Anri doesn't initially pick up on it, Mikado panics and says that he actually will accompany them tomorrow and that his errand can wait. Aoba is visibly pleased.
The next day, as Mikado wonders what to do about the apparent attack on Toramaru by the dollars, Aoba comes knocking on his door. As Mikado wonders how Aoba found out where he lived, he also notices that Aoba wasn't the only one there. Several thuggish looking individuals were also standing behind Aoba. He asks Mikado to accompany them, saying that it's very important. Not having much choice, Mikado follows Aoba and his thugs to an abandoned warehouse where he finally asks why Aoba took him here. Aoba immediately asks Mikado if he's wondering about the Dollars attack on Toramaru. Mikado asks how Aoba knew that and Aoba plainly admits "We did it." while still smiling. As Mikado absorbs this information, Aoba also says that, while they are all members of the dollars, they also go by the name "Blue Square" It is revealed that the reason Aoba attacked Toramaru so violently was due to the fact that they interrupted his tour with Mikado and Anri several weeks ago and he was just venting his anger. He and Mikado receive several messages from the dollars website about Toramaru attacking dollars members and Aoba says that it's finally started. Aoba then makes a strange offer to Mikado. He asks Mikado to become the next leader of the Blue Squares, intending to use him as a figure head like his brother Ran Izumii. He wishes to absorb the Dollars into his gang and bring the Blue Squares back to their former glory. Aoba says that they'll do anything Mikado asks of them, even if it meant sacrificing themselves to Toramaru. As Mikado denies this offer, saying that he could never order them around like that, Aoba steps closer to Mikado and claims that to be a lie, asking if Mikado knew he was smiling.
Dollars and Blue Square Arc
As Mikado tries to stall for time, Aoba is confused as to why Mikado hasn't made a decision yet. Despite his timid exterior, Aoba could sense the resolve Mikado could summon when the situation called for it such as with the incident with Yagiri pharmaceuticals or with the yellow scarves. Aoba soon comes to the conclusion that one of his long time enemies, Izaya Orihara must be involved somehow. He guessed that Izaya was trying to manipulate Mikado for his own reasons but Aoba refused to admit defeat. Aoba soon starts pressuring Mikado to make a decision by making subtle threats towards Anri. He says that if Mikado can't decide yet, Aoba can meet Anri while he stayed here to think about everything. Unbeknownst to Aoba, this action sparks a swirl of black emotions to form in Mikado's heart. The meeting is soon interrupted by the ringing of Celty's phone. With her hiding spot exposed, Celty walks into the warehouse but tells them not to mind her and continue. As Aoba wonders what the headless rider would want with them, Toramaru also bursts into the scene. Aoba identifies Mikado as the leader of the Blue Squares, which cause Toramaru to turn their focus onto him. Celty and Mikado run while Aoba and the Blue Squares hold off Toramaru on behalf of their "Captain."
After the fight, most of the Toramaru members were either beaten or went after Mikado while everyone in Blue Square stood victorious. While stepping on another man's face, Aoba contemplates what to do next and sends one of his members, Gin, to take one of Toramaru's bikes and follow Mikado. Aoba soon notices another bike, Vorona's (which was supposed to be bait for Celty), and finds a thin black thread attached to it. Out of curiosity, Aoba and the Blue Squares follow it. As they go along, Aoba gets frequent updates from Neko who is watching the fight between Toramaru and the Dollars as well as the fight between Anri and Vorona. Aoba soon develops an interest in not just Mikado but in Celty and Anri as well. After Toramaru retreats and the fighting dies down, Mikado calls Aoba back to the warehouse to discuss their agreement. Mikado expresses his desire to fix the dollars and decides that teaming up with Aoba is the best way to do that. Aoba is amazed at how easily Mikado is falling into his hands and begins making plans for the future. Aoba juggles different plans in his head including how to get Izaya out of the picture, how to manipulate Celty into working for him as well as how to make his move on Anri.
Mikado soon proposes a written agreement to make their alliance official. Aoba is surprised but figures that he expected as much from Mikado. When he looks at the paper Mikado gives him, several alarms ring in Aoba's head. It comes too late as Mikado stabs Aoba's hand with a ballpoint pen. As pain erupts through Aoba's arm, he turns to ask Mikado what was going on. Aoba's words die in his mouth when he sees nothing but a cold, piercing glare from Mikado's eyes. Mikado states that his reason for this are for putting Anri in danger as well as attempting to take control of the Dollars. Mikado orders Aoba to "stomach the full wrath of his anger." Before his men can react, Aoba tells them to back off. Aoba realizes that Mikado wouldn't back down - or let go of the pen - until he agreed. Aoba states that Mikado can use the Blue Squares however he wished and Mikado does a complete 180 in his personality. Mikado yanks out the pen and proceed to expertly treat and bandage the wound. Despite his docile and friendly personality, the fact that Aoba witnessed how flawlessly Mikado was able to switch between his two personas sends a chill down his spine. When Aoba leaves, he wonders in his head if Izaya had realized how they had underestimated Mikado and how he had far from shown his true nature. After all his planning, instead of the Dollars being absorbed by the Blue Squares, it was the Blue Squares that ended up devoured by the Dollars.
Aoba becomes Mikado's second in command as he begins his "Cleansing" of the Dollars, however, Mikado still suspects that Aoba wants to take control of the Dollars somehow. Most of the time, Mikado, Aoba, and the Blue Squares hunt down the "negative elements" in the Dollars (i.e. thugs who are simply using the dollars name as a scapegoat to increase their reputation) beating them up severely and banning them from the website. A flashback shows that Aoba went over to Celty and Shinra's apartment alone and attempted to make friends with Shinra but they were cautious since Aoba gives off the same vibe as Izaya. Shinra, in addition, threatened Aoba with a scalpel and warned him not to try anything that would put Celty in danger.
After the hunt for Kisuke Adabashi begins, Mikado and Aoba manage to corner him by Mikado posing as Ruri Hijiribe to lure Adabashi into a trap. While Aoba and the Blue Squares deal with his followers, Mikado opted to deal with Adabashi directly in order to take revenge for Shinra. After Mikado and Masaomi have a falling out, Aoba and the Blue Squares carry an injured Mikado to the hospital.
Aoba also joins the chat room at the invitation of Mairu and Kururi under the handle "Pure Water 100%" along with several others. Also, unbeknownst to Aoba, his brother, Ran Izumii, was recently released from prison, has joined up with Izaya, and is out for revenge against him.
Dragon Zombie Arc
Aoba is seen hanging out with Mairu and Kururi at the Raira Academy pool. The three of them discuss what Izaya has gotten himself involved with as he has been out of contact for a while even in the chat room (Izaya had switched to the alias "Chrome" without anyone knowing.) Aoba wonders in his head about how to get rid of Izaya but finds it hard to concentrate with the Twins in front of him. It's at this point that Aoba realizes that he has no idea how to act around girls at all. Eventually, the three of them part ways and Aoba gets a call from Gin. As they talk, Aoba realizes that Gin was talking on the cellphone while in the middle of another one of Mikado's missions. Gin is jealous that Aoba has two girls to hang out with and brings up the question of what Aoba would do if no one were close to him. Aoba ends the call and actually questions that possibility. Aoba shudders at the thought of being alone mostly due to the fact that he doesn't want to end up like Izaya who has isolated himself from even his own family. Aoba walks home, still wondering how to take Izaya down.
Kadota's Coma Arc
Ran also confronts Aoba at some point in the novel, but he spares him for some reason (likely because he has something else planned for him later). Aoba holds a Blue Squares meeting with Mikado and he tells the news about Kyouhei. Later he is shown with Mikado and Celty when Akabayashi comes in and asks them if they wanted to be allies with the Yakuza.
Hours after the talk with Akabayashi, Aoba is shown talking to a blue squares member in a van when the yellow scarves ran in the blue square's base. Aoba wakes up a big muscled kid named Hoji to beat the guys up. Later Aoba is yelled at by the other members of the Blue Squares because of his actions.
Showdown Atop Tokyo Hands arc
He was with Mikado when he got a phone call from Chikage. Mikado runs off to find his childhood friend and Aoba just walked off to the city. Then due to the slasher fest he is slashed by one of the people in the slasher army led by Takashi and Haruna.
Aoba is shown to have changed his appearance a little bit, and to still be friends with Mikado. He is now a senior in the third grade at Raira Academy and seems to be on good terms with the new Raira students. Before the beginning of the school year he becomes acquainted with Kuon and introduces him to the twins. After Kuon leaves, he warns the two to stay away from him or they could get into trouble.
Somewhere in an abandoned building, Aoba attends a Blue Squares gathering where he silently listened to Horada, who sat on a sofa, speaking about how important he was to Blue Squares in the past. Aoba speaks about how his seniors said that without Horada’s presence, the Blue Squares of today couldn't have been at all. Aoba then brings up that he always heard about him from his brother, which prompts Horada to become puzzled and question who Aoba’s brother is as he opens a can of beer in his hand. After revealing that his brother was Ran Izumii, he watches as Horada spurted out the beer he was drinking, and his face becomes green. Aoba speaks about how his brother is currently in the Awakusu-kai but tells him that he'll make his way to find Horada once he finds out that Horada is out of prison. Aoba then mentions that since Li-pei Ei returned to Dragon Zombie, they've been scuffling all this time. He asks Horada to be the Blue Squares backer so they could have confidence to upscale their fight into a proper war, but Horada tries to turn the offer down while breaking into a cold sweat and quickly leaving the building leaving Aoba and the other Blue Squares members. With Horada gone, Aoba and the other members begin to talk to each other regarding what happened to make Blue Squares die one time. Since Horada did not even know about Li-pei Ei and that he is pretty much an outsider already, Aoba decides that Blue Squares doesn’t really need him.
Aoba and his companions go out into the city late at night when he receives a message from Mairu saying that she and Kuon are looking for a girl named Ai Tatsugami and tells him to get the details from Kuon. Aoba then hears a rumor that someone had fought with Shizuo and gave him a few injuries. Doubtful of the rumors, Aoba checks the news on IkeNEW - an Ikebukuro information site he knew - and sees the video of the fight in question. While the video quality was poor, Aoba notices the boy fighting Shizuo wore a Raira uniform. Although he could not tell who it was, he does recognize Kuon in the background of the footage.
Suspecting someone hanging around Kuon to be the person fighting Shizuo in the video, Aoba approaches Kuon at Sonohara Hall and encounters Yahiro and Himeka. After seeing Yahiro's injuries and questioning him on how he got them, he concludes it is likely him. Later that day, he is contacted by Shinra, asking him about the Raira student Celty is looking for to which Aoba provides her name. The following day at school, he is approached by Yahiro. When asked if he knows anything about Kuon's disappearance, Aoba tells him he does not know but ends up giving Yahiro Kuon's address.
- The name Aoba means "fresh leaves," while the surname Kuronuma translates to "black swamp."
- The series' author, Ryohgo Narita, has expressed interest in writing a story with Aoba, Kururi, and Mairu as the leads.
- Aoba was originally supposed to be the main male protagonist of Durarara!! SH.
- His character song is called "Romantic Ga Tomaranai."
- He states in the eighth light novel that his favorite film is The Blair Witch Project.
- Aoba claims to be around the 600th person to join the Dollars but says that his name is not on the list due to the site going down and losing data.