Sleepy Ash (スリーピーアッシュ, Surīpī Asshu) or Sloth (怠惰, Taida), and mostly referred as Kuro (クロ) throughout the series, is the deuteragonist of Servamp. Kuro, named by his Eve, Mahiru Shirota, is the Servamp of Sloth. He is the oldest of the eight Servamps. When he is exposed to sunlight, he transforms into a black cat.
If Kuro is not in his cat form, he has shoulder-length, blue hair with his front bangs reaching his eyes. His eye color is red and he has big, dark bags under them. They are always half-lidded and express a feeling of boredom. Just like any other vampire, he has pointed teeth.
Kuro mostly wears a blue jacket which is a tad darker than his hair color with the hood pulled over his head, the black fur looking close to the one of his cat form. He also has a patch on his left shoulder with the Roman numeral 1, probably because he is the oldest of the seven sins. He is wearing the bell Mahiru gave him as their contract symbol around his neck as sometimes seen in official illustrations, which is apart from that mostly hidden under his clothes. His blue jacket is often buttoned open, either a simple black or white shirt hiding under it. On both sides, Kuro has chest pockets. The hem of his jacket splits into many threads, starting short at the front but grow in length as they reach his back. His white pants are skin-tight and held up with a red belt, which is rarely seen. Kuro wears long, black boots that almost reach his knees.
Hundreds of years before, Kuro wears long black hooded jacket with with white pants and darkish grey coloured suit underneath and a long scarf that he let loose.
As a cat, Kuro has black fur and red eyes. Around his neck he is wearing Mahiru's bell as a collar with red leather. His tail splits at its end into four, close to the threads at the back of his jacket in his human form.
Being the Servamp of Sloth, Kuro spends his time sleeping, lazing around or playing video games. He feels no shame in running away to avoid any trouble and refuses to take decisions for he doesn't want anything to be his fault, and he doesn't want to disappoint anyone. Kuro is a 'shut in' pacifist vampire, and rarely drinks Mahiru's blood, most of the time he refuses and drinks only when he is about to fight. He prefers staying at home rather than going out and seems to dislike the changes of temperature, according to him vampires are delicate to this.
Despite his lazy and at times comical nature (comical due to his laziness and arguments with Mahiru), he is shown to have a dark side. This is shown whenever anyone try to bring up his past that involves him killing the creator of Servamps. The mere mention of his past was enough to make Kuro who usually is nonchalant to become aggressive. He views himself as a monster, a fact that he dislikes, which caused him to refuse finding out more about his own race as it'll prove further how much of a monster he and his siblings are. He also refuse to turn any humans into vampires to make them his subclass, saying that they probably didn't want to become vampires, and that vampires shouldn't even exist.
Mahiru's straightforwardness and sincerity started to influence Kuro, though he always hides it by feigning being uninterested and lazy as always. After Mahiru confronted him in his mind regarding his past actions and assured him he is not alone, Kuro decides to stop running away and face his past, since then he has become more willing to fight and determined to stop Tsubaki.
He also prides himself in his cat form, often referring himself as a cute pet or super cute cat and such. He always uses his cuteness to benefit himself, such as to attract the girls in Mahiru's class to give him foods or snacks, and sometimes also tries to use it to calm Mahiru and his friends when he thinks they are worrying or arguing too much, telling them to calm down and be soothed by him, which unfortunately doesn't work for them (except for Licht who is fond of small animals) since they already knows Kuro's characters all too well.
Sleepy Ash is the first and oldest of the seven servamps. At one point in the past, he was approached by with the decision to kill a certain person, the creator of the servamps by the C3. He called his remaining siblings to a family meeting to discuss whether they should accept the request or not. The discussion became an argument so they decided to do a majority vote, with Sleepy Ash making the final decision. Believing that the experiment that their creator was doing was too dangerous and to prevent another "monsters" like them to be born, Sleepy Ash decided that they should kill their creator and he willingly volunteered to be the one to do it. This decision caused him to have a falling out with Lawless, straining their relationship for years.
As per request, Sleepy Ash went to Japan to do the job. Upon meeting his creator for the first time after hundreds of years, Sleepy Ash was surprised at the fact that the information was true, having a hard time believing that his creator is still alive. Sleepy Ash's resolve started to waver, but then convinced himself that his creator needs to be killed because his research is too dangerous, which he does. After killing his creator, however, Sleepy Ash began questioning whether he did the right thing or not, and this uncertainty haunted him since then.
Contract with Mahiru
Sleepy Ash first met Mahiru when the latter found him lying helplessly on street due to the heat and decided to take him in as a pet, naming him Kuro. Soon, Kuro revealed himself as a vampire to Mahiru. Mahiru accuses him to be the street slasher that he heard recently and will try to drink his blood, but Kuro denies his accusation. Kuro tells him that he will leave once it gets dark so until that Mahiru must not call his name while he is in human form. However, misunderstanding what Kuro meant by his name, Mahiru calls the name he gave to the vampire, forming a temporary contract with him, much to Kuro's dismay. To annul the contract, Kuro must not drink Mahiru's blood until 24 hours passed and they cannot be separated beyond the distance limit or else something will happen, but Kuro was too lazy to explain the detail. Without any choice, Kuro sticks with Mahiru, going shopping with his friends despite his protest that he can't deal with sunlight, to which Mahiru retorts that it's already noon so he should be okay. On their way back, they were suddenly attacked by a vampire named Belkia who is targeting Kuro.
Kuro kicks Belkia away before trying to run away, earning him a scold from Mahiru who tells him to help. Kuro simply replies that he can't stand against Belkia and he is one of people who thinks that someone else will deal with it. However, Kuro immediately changed his mind after watching Mahiru trying his best to save his friends, leading him to protect Mahiru. Kuro fought Belkia and powered up by drinking Mahiru's blood, finalizing the contract between him and Mahiru, making him a servamp. He easily defeated Belkia and intended to kill him, but Mahiru stopped him by reminding him of his own words that whatever happens onward, he (Mahiru) will be the one who make the decision and take the responsibility for it. Relenting, Kuro spared Belkia who revealed that he was ordered by a vampire named Tsubaki who hates him, but Kuro doesn't know anyone with that name.
First Encounter with Tsubaki
Tsubaki introduced himself as Kuro's youngest brother and the eighth servamp, the servamp of melancholy. However, Kuro doesn't recognise him as he never met him before and avoids fighting him, opting to run away. Tsubaki proceeds to attack Kuro, and despite the injuries, Kuro refuses to drink Mahiru's blood because he is too tired to fight back after using his strength against Belkia yesterday. They are saved by Servamp of Lust's interference, allowing them to escape.
Alliance with Misono and Lily
The next day, Kuro and Mahiru are taken by Misono Alicein, the Eve of Servamp of Lust that saved them before, Snow Lily. They demands Mahiru to give Kuro to them to fight against Tsubaki. While Mahiru objects since Misono and Lily are using force, Kuro quickly surrenders, forcing them to run away. After Mahiru and Kuro protected two of Lily's subclasses, they forms alliance with Misono and Lily. Mahiru and Misono gets into a quick argument regarding their respective servamps, which Kuro unsuccessfully tries to stop by using his cuteness. Despite this, both Mahiru and Misono quickly bonds due to Mahiru's friendliness, and when Mahiru asks Kuro how normal and important making friends is, Kuro simply says that he will only kill people who Mahiru tell him to kill and protect people who Mahiru tell him to protect, making Mahiru comments that Kuro has no independency.
Servamp Family Gathering
Shortly after forming alliance with Lily and Misono, the Lily decides to do a family meeting with the other servamps, giving Kuro and Mahiru the website address of vampire SNS where the subclasses of servamps are telling their troubles regarding Tsubaki's action. As he has said, Lily puts the location and time where the servamps are going to have a meeting, which is at a nearby family restaurant. Kuro tries to excuse himself so he doesn't need to go, but Mahiru forces him to go anyway. At the promised place, Kuro is confronted by Servamp of Gluttony, World End, who angrily asks him where he had been hiding for the last hundreds of years and demands to treat him all of the foods, which Kuro passively ignored. Servamp of Wrath, The Mother, then greets Mahiru whom she mistook as Kuro, with the latter telling her she's got the wrong person.
During the meeting, the servamps decided for Mahiru to be the leader and responsible of gathering the servamps. Lily then informs Mahiru that Kuro can give him a weapon to fight, much to Kuro's annoyance who wonders if Lily purposely holding a meeting so he can reveal that to Mahiru. When prompted by Mahiru, Kuro asks what does he need a weapon for. When Mahiru answers he wants it to protect himself and his friends, Kuro tells him to close his eyes as he materialize his weapon which is called "Lead", that takes a form of a broom. Kuro reminds Mahiru that when they first met, Mahiru attacked him with a mop and asks does he think cleaning tool equals a weapon, something that Mahiru denies.
Battle Against Sakuya and Belkia
Mahiru and Kuro are lured by Mahiru's close friend, Sakuya, who is revealed to be Tsubaki's subclass. Kuro and Mahiru are bound by another of Tsubaki's subclass, Otogiri's string, but Kuro able to free himself to shield Mahiru from Sakuya's attack before being stabbed down by Belkia's swords. When Mahiru calls out to him to drink his blood, Kuro tells Mahiru that it's useless for him to drink his blood now. He explains that servamps receives strength and motivation by drinking their eve's resolve flowing in their blood. Since Mahiru is unsure right now, even if he drinks his blood, it won't be enough to defeat both Belkia and Sakuya.
When Mahiru decides to fight Sakuya after the latter injured Misono who came to help them, Kuro tries to stop and tells Mahiru to retreat before he do something that he will regret, sensing that Mahiru is still unsure of himself. As Mahiru attacks Sakuya, Mahiru's doubt and fear starts to overflowing within Kuro, causing him to instinctively drank Mahiru's blood and lose control of his power, almost engulfing Mahiru. Before he can completely absorb Mahiru, Kuro is stopped by Servamp of Envy, Jeje, who shoots him several times until he changes back into his cat form.
The next day, Kuro asks the depressed Mahiru whether he is going to school or not and offers to play game together to get him to respond, but was taken aback when Mahiru instead asks about his injuries. Kuro then asks does he regret picking him up, when Mahiru tells him to shut up, Kuro is convinced that Mahiru is regretting it. Mahiru then takes him to eat at sushi bar where his uncle is working and meets Tsubaki by a chance. After Tsubaki tells Sakuya's story, he senses Kuro's murderous intent, who is hiding inside Mahiru's bag, prompting Tsubaki to leave. At the day of school festival, Kuro is thrown by Mahiru to stop Sakuya who was visiting the school, and after talking with Sakuya, Mahiru tells Kuro that he wants to stop Tsubaki so they need to become stronger together, making Kuro wondering whether they can face Tsubaki or not though he doesn't object Mahiru's decision.
A month has passed, Mahiru still tries to train using his Lead properly while Kuro was playing a game. Mahiru demands Kuro to drink his blood so they can train together, but Kuro refuses. Mohair then apologizes for losing control of his power and want to become stronger. Kuro replies that they don't have time for that and he can't handle the responsibility that comes with it. Mahiru then realises that Kuro never wants to drink his blood, only drinking it when fighting and instead eat normal human foods. Mahiru tells Kuro to tell him if he ever want to drink his blood, but Kuro simply replies that he doesn't want to drink it. Kuro then opens the vampire SNS, only to find it has been shut down.
On their way back, they are chased by a vampire, but it turns out that the vampire is actually running away from Mikuni and Jeje who are chasing after him and then kills him. Mahiru immediately bends on his knees, asking Mikuni to teach him to fight, prompting Kuro to tell him to lift his head, which Mahiru refuse. Mikuni then introduces himself as Misono's older brother, shocking Kuro and Mahiru. They continue their conversation at a restaurant where Mikuni reveals that Kuro is not only the oldest, but also the strongest servamp, much to Mahiru's doubt and Kuro states that he is only a cat. Mikuni then shifts the subject about the vampire SNS, having contacted the ones managing it and it turns out the website belonged to an institution. Hearing this, Kuro becomes uneasy and drops his drink, surprising Mahiru. Not wanting to hear more, Kuro goes outside, excusing himself by saying he will smoke. Mikuni states that as one of the highest rank vampire, Kuro must have bad experience with the institution.
Outside, he is approached by a researcher belongs to the institution who asks for his cooperation, which Kuro coldly turns down, so the researcher left the letter to him. Lily then appears besides Kuro, commenting it reminds them of their old days. Kuro questions Lily's presence alone, to which Lily answers that he is called by Mikuni. When he returns inside with Lily, he returns just as Mahiru says to Mikuni that he will become stronger and he and Kuro will become real partners, surprising Kuro. Mikuni, Lily, and Jeje then agrees to help Mahiru becoming stronger, much to Mahiru's happiness. Seeing this, Kuro decides to hide letter from Mahiru.
Meeting Tetsu and Old Child
At school, Mahiru and Kuro overhears some people were talking about Kuro whom they referred with his street name, something that only known by people involves in vampire business. When Mahiru tries to catch up the person, he bumps into his senior Shuhei Tsuyuki who appoints Mahiru to help in summer festival holds by their school town. After school, while Mahiru helps with the festival, Kuro quickly enjoying himself by buying lots of foods from the stalls. While waiting for the fireworks, Mahiru laments how he thought that Shuhei is a vampire but turns out he was wrong, prompting Kuro to comment that being suspicious of people is not like him at all and he is fine with the way he is normally. However, Kuro quickly retracts his words, since Mahiru being suspicious of people will prevent him from doing reckless things. They are approached by a man who asks Mahiru to take the silver case he found to lost and found stall. Mahiru decides to take the silver case to the stall as Kuro warns him that they mustn't get too far away separated.
Not long afterwards, explosions occurred, which originated from the similar silver case that Mahiru was carrying, so Mahiru quickly calls out for Kuro, who drinks his blood and jumps to the sky, throwing the silver case so it will explode without causing any casualties, but Kuro threw it too fast. Kuro assures Mahiru it will be okay since it will usually being blown by wind, but unfortunately, it fell straight down. Before Kuro could catch and throw it again, Tetsu Sendagaya, a person who Mahiru meets a few minutes ago at the festival, caught the bomb into his coffin where it exploded inside without destroying the coffin. Tetsu reveals himself to be the Eve of Servamp of Pride, Old Child, who now goes by the name Hugh.
At Mahiru's apartment, the four of them continues their conversation where and Tetsu and Hugh agrees to accompany Mahiru and Kuro on their training with Mikuni, making Kuro comments that it's a pain because they're getting friendly with each other that most likely due to both Mahiru and Tetsu are plain. Meeting Mikuni to train, Kuro decides to play his game, leaving Mahiru and Tetsu to train alone. When Mahiru is questioned regarding knowledge about vampires and humans by Mikuni and Hugh, Mahiru answers that he prefers to hear about if from Kuro himself since he is his partner, surprising Kuro who then replies that it's too much to handle. The training ends once Tetsu uses his full power to remove all of Jeje's paper bags, the impact of the attack was enough to nearly blow away Kuro and Mahiru. Tetsu's strength makes Kuro feels that he is not needed in the training, making him glad.
The next night, the training was cancelled due to one-sided hostility between Misono and Mikuni, so Kuro and the others decides to go to a family restaurant to discuss about their next move, though they are side tracked by the restaurant menu for a moment. When Mahiru suggests they ask the neutral organization, C3, for help, Hugh and Lily are against it due to what happened in the past when they received request from C3. Kuro quickly ends the conversation by saying that's not important right now. Kuro's interruption surprised Mahiru, but decides not to press the question further and they end the topic. Hugh and Lily then reveals that for the three days ago, Tsubaki had bombed 13 places related to C3, one of them was Mahiru's school. The news urged Mahiru and Kuro to go see the school that has been destroyed, which greatly shocked them before they are knocked unconscious by two C3 members.
Captured by C3
When he came to, Kuro finds himself at C3 base, accompanied by two of its researchers who demands for Kuro's cooperation. Kuro questions where Mahiru is. The researcher tells him that Mahiru is in another room and if he agree to help C3, they will release his eve. When the building was shaking, Kuro realises that Mahiru has escaped by himself, so refuse to cooperate and tells them to never force Mahiru into anything annoying again. Kuro lands right below where Mahiru has escaped. He quickly tells him that they're leaving, but Mahiru says there's something that picks his curiosity. Kuro says he is not curious, so he'll be taking his leave, forcing Mahiru to drag him to listen and they need to find the exit anyway.
Finding a map, the map doesn't show a way out, distressing Mahiru. Mohair then asks Kuro about the abnormality that he experiences when they were separated. Kuro explains that if servamp and eve for separated beyond the distance limit for six hours, the eve will experience such as numb limbs, headaches and many more, and if eighteen hours passes both of them will become a cat, and finally if twenty four hours passes, the eve will die. Mahiru asks is there anything else he hasn't told him. Kuro tells him that there are many things he hasn't and probably will never tell him because Mahiru will stick more into vampire business which is annoying. Trusting Kuro, Mahiru respects Kuro's wish not to ask him and tells him not to forget that they are partners so if he is in trouble he will help him. While he is happy with Mahiru's understanding, Kuro decides to play it off by turning into cat and says it's annoying.
Mahiru then explains that Tsubaki used to be in C3 and they may find out more about Tsubaki if they search through the reference room, an information that disturbs Kuro. The two decides to separate: Kuro looks for the exit while Mahiru looks for the reference room. Kuro tells Mahiru to yell if something happen so he can get away, annoying Mahiru who retorts he should be saving him and also yell if something happen. Kuro's inner self then points out Kuro's happiness after hearing what Mahiru told him and his nervousness if Mahiru finds out what happened in the past and the possibility that Mahiru will still trust him even if he knows what happened. He continues to points out how Kuro's actions and words are contradictory and suggests they break down C3 while they are inside the base since both of them hate it, at though which made Kuro feels uneasy.
Hearing a gunshot, Kuro intimidates Shuhei Tsuyuki from behind before turning into his cat form to pick Mahiru. Shuhei tells Mahiru how much of a monster vampire is and they cannot be trusted, but Mahiru simply tells him the good side of vampires he has seen and to him they are his comrades that can protect people. While Mahiru thinks it's a simple thinking, Kuro comments it's more like Mahiru bulldozing rather than being simple, and he hate it with all his might, leading to another childish argument between the two. Shuhei decides to let the two of them go since they can't convince the Sloth Pair. When they got out, Kuro and Mahiru realises they are in front of the elevator at nearby station.
Mahiru's classmate, Suzuhara, comes to Mahiru's apartment to return his cell phone, but it turns out she is possessed by a Djinn, an underclass creature that glue itself to humans and lead them to any nearby vampire to give the human to them to eat. In this case, the Djinn leads Suzuhara to Kuro for him to eat. Since Kuro doesn't want to drink blood, Mahiru exterminates the Djinn with his Lead. However, there are still more Djinns waiting in front of apartment, which Mahiru quickly exterminates before there are more victims. The extermination exhausts Mahiru who is carried by Kuro on their way to meet Tetsu and Hugh. Kuro explains that the mist around the town are also Djinns and cannot be seen by normal people.
Tetsu and Hugh who were looking for the Sloth pair meets them by a chance and Hugh reveals that since yesterday the amount of Djinns appearing are unusually high and Djinn can only be killed by the Lead of an Eve, so there's nothing that Kuro and Hugh can do. They re confronted by Belkia who is about to drink a blood of woman possessed by a Djinn. Before he can do so, Kuro saves the woman by cutting off Belkia's arm, but Belkia reveals his hand is still intact. He then reveals their plan to unleash huge amount of Djinn from servamps and about to attack Kuro, but he suddenly vanished. Due the direness of the situation, Mahiru decides it's the time to gather all seven servamps.
Ambush on Alicein Mansion
Kuro and Mahiru are invited by Tetsu who allows one of rooms at his family hot spring hotel to be used for their gathering. Mahiru drags Kuro to do a patrol with Tetsu and meets Yuri, one of Lily's subclasses who asks for their help to save Misono because he is in trouble. At Misono's house, they are not allowed to meet Misono until Tetsu threatens them as suggested by one of the servants, Dodo. Finally allowed inside, the three are welcomed by the head servant, Yamane. Kuro becomes playmate to Lily's subclasses who feeds him lots of sweet until Misono's father, Mikado Alicein, approaches them and starts to show the pictures of Misono when he was a child. Mikado won't allow them to meet Misono out of fear of his son's safety, and when Mahiru refuses, they decides to use force. Yamane attacks Kuro and pins him to the wall while the vampire is in its cat form, but after a bit struggle, they're able to meet Misono who tells them to give him some time to talk with his father.
Three days later, worrying about Misono who hasn't contacted them since, Kuro, Mahiru, Tetsu, and Hugh goes back to the Alicein house but then finds the house overflowed with Djinns. Tetsu throws Kuro and Mahiru to the house ahead of him, bumping into Otogiri who was ordered by Tsubaki and succeeded destroying Lily's contract item. Tsubaki tells them his plan to destroy all the contract items of his siblings to not only weaken them, but also to unleash huge amount of Jins. Mahiru states that he never give Kuro anything, but to Mahiru's dismay, Kuro reminds him by showing the bell that he gave to him when they first met. Kuro and Mahiru arrives at the place where Lily and Misono are, witnessing Lily absorbed Misono due to losing control of himself, horrifying them. Kuro assures Mahiru that Misono is still alive inside Lily. Knowing this, Mahiru prepares to attack, but Kuro stops him because the vampire is the one who supposed to attack and Mahiru can't do anything against him. Kuro quickly gives up when Lily's attack almost hit him, scaring him, but he prepares to attack again when Lily charges onto Mahiru who blocks the attack with his Lead as he calls for Misono to come out.
After freeing Misono and Lily returns to normal, Kuro is forced to get lots of towels to help the subclasses who are suddenly went ill. After Lily awakes, Kuro asks for Lily's help to tend his subclasses as Mahiru warns him not to strip, but was surprised when Lily tells that stripping is not his thing and he even want to cover his body even more, which is unusual for Lily. Mahiru points this out, but Kuro reminds him that it's a common sense not to strip in front of people, something that Mahiru confirms but coming from Lily is just not normal.
After finished helping the subclasses, Mahiru starts to think that he should give a stronger contract item for Kuro so it won't be easily broken, but when Tetsu tries to destroy Kuro's cat bell, it remains unscathed, much to Kuro and Mahiru's relief who thought it would be destroyed. Hugh reveals that as long as the trust between servamp and eve is strong, it won't be easily broken. Mahiru comments that as vampires, they ought to know about themselves, but Kuro reveals that they don't want to know because it's not fun at all to find proofs of how much of a monster they are. Mikado then thanks them as he reveals about Misono's past and shows how much he thinks Misono is still a child. Mahiru questions when Mikado is going to stop treating him as a child, which lead Mikado to leave in hurry, prompting Kuro to comment that Mahiru knows how to meddle into other people's business.
Meeting Licht and Lawless
After the incident at Alicein mansion, Kuro and the others are gathering at KTV after Hugh's subclass informs them there's a suspicious person who is strong enough to severely injured a subclass. When Hugh's subclass informs of the person's location, Mahiru and Kuro follows him. The person gives Kuro a dangerous vibe, so Kuro suggests that they should not get involved before noticing a hedgehog inside a cage the person is carrying which Kuro recognised. Mahiru then asks does Kuro has any subclass. Kuro explains he doesn't have one because it's too troublesome since he can't tell if the human still wants to live or not. Hearing Kuro's opinion for the first time, Mahiru tells Kuro that he will always believe in him so he should put more some efforts to be more open up. Kuro looks troubled by this statement while saying that it should be Mahiru who work hard.
The person they are tailing finally face them, already noticing they are following him. He then immobilises and attacks Kuro with his Lead. Kuro notices his wounds are healing very slowly and is about to be attacked again if Mahiru didn't save him. He drinks Mahiru's blood and ties his attacker with his jacket tails, but the person easily frees himself. The hedgehog then interferes, introducing himself as Servamp of Greed, Lawless, while the attacker is his Eve, Licht Jekylland Todoroki. Lawless quickly refuses to ally himself and Licht with Mahiru and Kuro, instead telling Mahiru that if Kuro just make a decision, it can end at once by using a majority vote like they had done before, something that upset Kuro. Lawless continues to mocks Kuro that the latter hasn't change in a bad way, causing hostilities between the two. Lawless then comments that Pride, Lust, and Envy are on Kuro's side, and he doesn't want to get stuck on their side. Kuro retorts that Wrath and Gluttony are also present at the previous family meeting, to which Lawless simply replies that the two servamps are not so smart but he is sure they haven't forgotten what happened.
Back at the lodging, they sees Licht appearing on TV as a famous pianist overseas, so Mahiru decides to try meet Licht by going to his concert, be he doesn't have any ticket to enter. Light's manager, Kranz Rozen, helps them in by giving a ticket stub. On their way, they spotted Otogiri, prompting them to go to the concert hall to stop the fight before it's too late, only to find Lawless has killed all of Tsubaki's subclasses that were sent to kill him and Licht. Lawless then attacks Mahiru after being annoyed by the latter's insistence they should work together, and Kuro protects him before he could hit the wall.
Lawless then starts to reveal their past when they received a request from C3 to kill a certain someone that they decided with a majority vote, and Kuro was the one who made the final decision. As Lawless is telling this, Kuro starts to unleash his blood thirst. Before Lawless could reveal Kuro's decision, Kuro snaps and fight occurs between the two. They are stopped by Licht who kicks Lawless and immobilized Kuro using Mahiru's Lead. When hearing Licht's piano play, Kuro starts to have vision of his past that makes him depressed and unresponsive for the rest of the day no matter how many times Mahiru calls for him, going as far as indirectly intimidating Mahiru when his eve tried to ask about his past.
Trapped Inside Black Sphere
Hearing that Lawless has gone missing and deduces that Tsubaki was the one responsible, Mahiru brings Kuro to look for Licht who is weaken due to being too far away from Lawless. Seeing Higan's flame, Kuro tells Mahiru to wait until Tetsu and Hugh came since it's too dangerous with just the two of them, but Mahiru insists that Kuro will be okay and they might be too late if they're waiting. When Kuro is about to fight Higan, however, black substances suddenly comes out from his body and he is trapped inside a small black ball that also causes Mahiru's Lead to disappear, rending neither of them unable to fight.
Fortunately, Kuro is revealed to be all right despite being trapped inside the ball even though he doesn't know what the cause is. In fact, he is seemingly content with staying there since he can't stand with the current situation, something that doesn't sit well with Mahiru who insists that he will find a way to free him. Both Mahiru and Tetsu attempts to free Kuro from the ball by using a saw and a hammer to destroy it, but none of it works and only makes Kuro freaks out and feels uncomfortable due the sounds it made. Mahiru then tries to use a holy water that he got from Kranz, but this also proves ineffective and only made Kuro feels worse since vampire cannot stand holy water.
Mahiru decides to bring Kuro to Mikuni, hoping Mikuni knows the way to return Kuro to normal. At Mikuni's antique shop, they are instead welcome by Johannes Mimir Faustus, a researcher and acquaintance of Mikuni who is interested in researching Kuro before Mikuni appears. Since there had been no case like Kuro, Johan and Mikuni sends Mahiru to Kuro's mind, witnessing his memories. It's revealed from his memories that Kuro has been haunted by uncertainty and regret for killing the creator of Servamps. Kuro mumbles to himself, trying to convince himself that he is not wrong and begs for someone to tell him the same. Finally knowing Kuro's problem, Mahiru tells Kuro that he is wrong for averting his eyes from his problem and convinces him to face it instead of running away, assuring Kuro that he will be there for him. Finally found peace, Kuro changes back to normal, determined to never repeat the same mistake again.
Rescuing Lawless and Licht
Kuro takes the form of a giant black lion and infiltrates the hotel where the other servamps and eves are fighting against Tsubaki's subclasses. Kuro and Mahiru works together and easily defeats the subclasses before going to where Lawless and Licht are who have just defeated Higan. Kuro takes this opportunity to mend his bond with Lawless, thanking him for not forgiving his action as that's what urges him to finally face the Greed servamp. Lawless was taken aback but thanks him back as well, both decides to settle the situation from now on. Mahiru and Kuro then asks for Lawless' current name. Lawless initially embarrassed to tell them, but finally tell them after much insistence by showing a handmade necklace with the name Lawless engraved on it that Licht gave him.
Their cheery moment didn't last long as Lilac snatched Lawless' necklace as a revenge against Lawless for killing his friends. To make things worsen, Tsubaki appears beside Lilac, taking Lawless' contract item as he revealed he has defeated Hugh. Kuro attacks Tsubaki who turns out to be an illusion and takes back the necklace, but the real Tsubaki then appears and snatches the necklace once more and destroyed it, causing Lawless to lose his power. As Tsubaki tries to attack Lawless, Kuro protects the latter as he tells Tsubaki that he now has accepted the fact that Tsubaki is indeed a Servamp like him since there's only one person who could created monster like them, which Tsubaki confirms to be the person he calls "Sensei" whom Kuro had killed. Kuro tells Tsubaki that if his goal is to avenge their creator, then he should point his hatred only to him instead of all seven Servamps since he alone was the one who killed their creator. Not wanting to regret anything again, he tells Tsubaki that he has decided to face him so they should be exchanging words and not weapons.
However, Tsubaki dismisses this by saying that the burden of Kuro's regret is too light. Tsubaki then questions why Kuro killed their creator, which Kuro answers it's because his research was too dangerous, however, Tsubaki reveals that C3 are continuing their creator's research. Before Tsubaki can reveal more, three members of C3: Tsurugi, Yumikage, and Jun arrives and quickly corners Tsubaki with their teamwork. Before Yumikage can shoot the cornered Tsubaki, Kuro prevents him, giving Tsubaki a chance to injure Tsurugi and escapes with Lilac with Higan's help. C3 then takes over the situation, taking the Servamps and Eves under their custody and protection, forbidding them to leave their house until further notice.
Detained at C3 Tokyo HQ
A few weeks later, it's snowing despite still in August, causing Kuro to cover himself with blanket and asks for much thicker blanket. Lawless and Licht, who stays with him and Mahiru for the time being since the incident under C3's supervision, also demands the same. Kuro and Lawless momentarily decides to relax, but Mahiru tells them to focus on their problem at hands regarding Tsubaki and C3. Lawless reveals that World End and The Mother are in Japan at the moment, around Tokyo to be precise, which surprises Kuro who thinks it's not a coincidence for all Servamps to be in the same town at the same time, thinking that the C3 are also behind this. They are then picked up by Tsurugi, Jun, and Yumikage who takes them to C3 Tokyo branch so they can be monitored more thoroughly and they don't have a say in the matter. While Licht and Lawless are lured to the base directly, Kuro and Mahiru are taken by the trio for lunch together.
After lunch, Kuro and Mahiru witnesses the C3 trio on their mission to catch nearby subclasses, though Tsurugi ended up killing nearly all of them except one, an action that horrified Mahiru. They then picks up Jun's son, but since the car won't fit, Jun decides to take back Kuro and Mahiru first. Entering C3 base, they are required to fill a profile and finds themselves unable to move from the chair they are sitting until Mikuni and Jeje arrives. When Mikuni meets Tsurugi, Mahiru asks Tsurugi to stop killing the subclasses, which Kuro supported by telling them that Tsubaki maybe willing to talk. Unfortunately, Shuhei dismisses this request, stating that vampires' words means nothing in C3. This conversation once again lit up hostilities between Mikuni and Tsurugi and a fight ensues between the two that results with Tsurugi attempting to attack Mahiru after unable to control himself. Kuro quickly defends Mahiru, giving Tsurugi the opportunity to attach some sort of collar that will enable Tsurugi to choke him at will, but since he doesn't want it comes to that, he tells Kuro to get along with him. Kuro initially refused, but reluctantly agrees after Tsurugi said he won't take off the collar until he dies.
Mikuni launches another attack, strangling Tsurugi with his Lead and nearly killed the magician until Kuro cuts the thread connecting to the Lead, saving Tsurugi. Shuhei takes Kuro's action as an attempt to kill Tsurugi, ordering the latter to restraint Kuro. The Servamp tries to explain to Shuhei that he has no intention to defy C3 as long as they can capture Tsubaki and he can converse with him, but Tsurugi points out Kuro's doubt in them by asking will the Servamp believe him if he say they will take care of it. Tsurugi then leaves to get some stuff he forgot while Kuro and Mahiru are waiting for him. Kuro tells Mahiru that he won't let C3 do as they please and Lawless has finally made him realised that he doesn't want to regret again so he asks Mahiru to lend him a hand so they together with all the Servamps and Eves can fight against Tsubaki, which makes Mahiru happy and agrees with no hesitation. The two then tries to think up of their next moves, but Kuro can't think of anything due to the fact that C3 couldn't careless about vampires and then wondering where Licht and Lawless are. Tsurugi then comes back, removing the restraint from Kuro and thanks him for saving him.
Wishing to make some members of C3 to understand them, Mahiru asks Tsurugi, Jun, and Yumikage to take them on their missions, which approved by Jun. Two days since their stay, Kuro and Mahiru are observed by Tsurugi, the Sloth pair watches the magician apologising to everyone who is angry at him even before they say anything. From this, Kuro states that he learn that no matter he do he will be forgiven if he apologise cutely, apologising to Mahiru in his cat form for eating his potato chips, which only made Mahiru annoyed. When Mahiru asks does Tsurugi do any combat training, Tsurugi asks back is he strong, which Kuro answers that Mahiru is strong, but Tsurugi changes the subject and decides to make one hundred paper cranes. Tsurugi then tells them to do some exercise to make their body flexible. Kuro, however, has a hard time to get the exercise right since his body is stiff. They are then taken to a training room where Tinker gives Tsurugi, Yumikage, and Jun new weapons. Tsurugi tests one of the weapons on Kuro, turning him into a cat. The Tinker explains that the weapon Tsurugi was using is capable of shooting artificial sunlight.
They are interrupted by an alarm, causing Tsurugi's mind to go unstable and he suddenly attack Kuro. Before it get worse, Jun and Yumikage had Tinker to stop the alarm. Tsurugi and Kuro are then allowed by Jun to meet the other Servamps and Eves. Finally meeting Lawless and Licht, the Greed Servamp angrily yells at Kuro for not coming sooner. The Servamps and Eves discusses what happened so far, with Misono revealing that Lily's condition has gotten worsen and Lawless and Hugh may share the same fate if they're left alone, worrying everyone. Jun offers to help them recovering their powers in exchange they help them save Tsurugi. Not having any option at the moment, Kuro agrees and convinces Lawless to cooperate for now.
A few days afterwards, several subclasses manages to escape from their confinement, alerting Kuro and Mahiru to take actions before the subclasses can be killed. Kuro and Mahiru confronts Tsurugi who is ready to stop the subclasses, but Touma informs them that the subclasses are most likely trying to free The Mother who is imprisoned in the same base like them, surprising Kuro. The Mother is imprisoned to avoid her going rampage, but Kuro dismisses this possibility because The Mother is not the type to get angry without a reason. Touma orders Tsurugi to apprehend Kuro and Mahiru, prompting Tsurugi activates Kuro's restraint, preventing him from fighting and he can only watch Tsurugi subdues Mahiru who momentarily goes unconscious.
Not long after Tsurugi left after defeating Jun who came to help, Lawless, Licht, Tetsu, and Hugh finds them through the hole made by Tsurugi. Explaining the situation to them, the four agrees to help. While Tetsu and Hugh takes Jun to medical office, Lawless and Licht goes to ask for The Mother's help. While waiting for them, the restraints suddenly disappears, freeing Kuro and Mahiru. Since Tsurugi said that the restraint can't be taken off unless he dies, Kuro and Mahiru have a bad feeling that something has happened to Tsurugi.
- Kuro can change into a black cat and into his human form at will. He can also speak when he is in his cat form. But, when he is exposed to sunlight, he automatically reverts back to his cat form. It is later revealed that he can turn into a giant lion, though Kuro states that it took huge amount of energy to change into his lion form.
- When he drinks Mahiru's blood, the chain connecting them is visible and he receives power ups.
- He can extend his nails into long, sharp black claws, easily able to cut and skewer people and other vampires.
Speed and Flight
- He is shown to have incredible speed and can jump high very easily, also shown that he is able to fly.
- Since he is immortal, he can't die. But, he heals very quickly and he was still able to fight even when he was stabbed through with a sword and still stood protecting Mahiru when he was being slashed at back and forth by knives. He was also knocked out by being shot at in the back by Envy's barrel guns.
- When his control of his power was gone, he was much more faster, powerful, and ruthless; also unaware of what he is doing. He was shown beating Belkia, one of Tsubaki's servants, mercilessly. He grabbed Belkia's hair and was about to bite off his neck to kill him, revealing a new set of long, sharp canines, and he would have too if Mahiru hadn't stopped him by pulling on the chain around his neck and Envy knocking him out with his gun. He even hurt Mahiru in the process; grabbing his face with his claws, leaving three thick scratch marks above his right eye, and roughly biting him down on his neck.
- He can hardened, move and use the tails at the end of his jacket to fight. From this jacket, he can also produces black spikes that stabs through his enemies.
- Strength: 6/10
- Tactics: 5/10
- Cooperativeness: 2/10
- Mental: 3/10
- Appearance: 8/10
- Soothing: 10/10
Mahiru Shirota (Eve)
For hundreds of years Kuro didn't have an Eve until Mahiru picked him up thus making them partners. Kuro initially only sticking around Mahiru due the contract made between them, and whenever he does something, mostly it was because Mahiru forced him to do it. Both often get into argument due to their contradicting personalities. Slowly, however, Mahiru's determination and sincerity started to influence him. Despite continuously saying that it's troublesome or he can't face it, he always protects Mahiru. He was often baffled by Mahiru's straightforwardness and willingness to trust him that he usually hides by feigning lazy, while in reality he is actually happy. Even though not shown clearly, Kuro grow to care for Mahiru and doesn't want to lose his trust. Their bond improved further after Mahiru helped him confront his past mistake and for the first time he tells Mahiru directly they are partners.
Out of all his siblings, Kuro had a bad relationship with Lawless. Their hostility for one another originated when Kuro decided to kill their creator, something that Lawless strongly opposed. Unable to accept Kuro's action, Lawless told him that he will never forgive him, which continues for years. Whenever they met, Lawless always mocks and satirised Kuro's past action, which enough to make Kuro who usually prefers to be quiet to attack Lawless without any hesitation and shows clearly his murderous intent. Kuro doesn't blame Lawless for his hatred against him as he understands, but this doesn't stop him from attacking Lawless if he tries to bring up the past. After Kuro decided to face his past mistake, Kuro apologized to Lawless regarding the incident by thanking him for not forgiving him back then, which Lawless accepts. Since then, the two spent their times together more often and it's also revealed that both were quite in common, both often likes to annoy Mahiru with their antics in particular.
The Creator of Servamps is the one who made Kuro a Servamp. From what the other Servamps said, the creator was supposed to be a special person for Kuro, which implies that Kuro and the creator used to be close. Despite this, Kuro thinks that his researches, creating vampires in particular, is deemed too dangerous for Kuro, which led to his decision to personally kill his own creator. This was most likely due to Kuro's belief that the creation of monsters like vampires is not a good thing and he never once felt glad of becoming one. However, when before he killed the creator, Kuro was hesitant and then crying as he killed him. This left a feeling of uncertainty within Kuro, and soon became regret that continued to haunt him for hundreds of years afterwards, making him questioning his own action. This shows that despite thinking that he is dangerous, Kuro actually still cares for his creator and regretted for immediately choosing to kill him rather than speaking to him first.
Kuro is shown to have a strong hatred for C3, the neutral group, due to the request given to him to kill his creator. Any conversation regarding C3 always makes Kuro uneasy, even yelling at Mahiru when he suggested if they could get C3's help. Since the incident, he decides to avoid any involvement with C3. Later on, when Kuro and Mahiru were captured by C3, and were escaping, Kuro's inner demon that controls his power was taunting him by saying that C3 brings back bad memories and that they should trash something up since they both still really hate C3. After C3 saved him and the others from Tsubaki and watches over them since then, Kuro decides to temporarily work with C3 to make sure they won't do as they please.
Tsubaki bears one-sided hatred against Kuro for not knowing him being his youngest brother like his other siblings, mercilessly attacking him during their first encounter. Tsubaki actually has been looking for Kuro ever since he saw his lion form after he killed their creator, but didn't know it was him until Kuro showed up with that form together with Mahiru to rescue Lawless. Kuro initially didn't pay much attention towards Tsubaki and didn't really accept him as his youngest brother since he never heard of him. This changed after Tsubaki destroyed Lawless' contract item and revealed that he had witnessed Kuro killing their creator, forcing Kuro to believe that Tsubaki is truly a servamp. Coming into conclusion that Tsubaki's goal is to get revenge on him and his other siblings due to what happened to their creator, Kuro feels responsible and determines to stop and properly speak with Tsubaki to understand him, not wanting to repeat the same mistake he once done.
- "Ahhh...Now you're happy. Silly cat...Mahiru made you feel good...Right? But C3 brings back bad memories. If Mahiru discovers the 'Incident'...Will he still trust you? Are you worried? Mahiru's still a rookie...Happy birthday! You contradict yourself. You keep it all inside. You poor, pathetic boy! While we're at C3...Wanna trash something? After all, we still really hate them! Am I right?" (Kuro's inner demon taunting Kuro.)
- "What you call simple, I call nagging." (to Mahiru.)
- "Cat abuser." (to Mahiru)
- "Paranoia's not my thing...Unlike you. Why look for trouble?" (to Mahiru)
- "Look at me guys...My cuteness will calm you..." (to the arguing Misono and Mahiru)
- "Are you ever sorry...you found me...?" (to Mahiru)
- "The pain! Wish I could die...But I can't." (Kuro complaining after escaping Tsubaki)
- "Well, that's that! You are my master." (to Mahiru after drinking his blood, completing the contract)
- "You'll...be the death of me." (to Mahiru after being stabbed to protect Mahiru)
- "You are such a pain..." (to Mahiru)
- "Close that! I hate sunlight..." (to Mahiru)
- "I'm just your friendly neighborhood vampire." (to Mahiru)
- "Humans are soo cruel...Meanie!" (to Mahiru)
- "But the sun will kill me! Okay, I'm immortal. But still! Meeow!" (to Mahiru)
- "We mix like oil and water." (to Mahiru)
- "Reeeowr! Shame on you! Sucking up your cute little pet!" (Kuro complaining after Mahiru used the vacuum on him)
- "Vampires don't age...Plus, I have a baby face." (Kuro to Mahiru)
- "She hit me with a broom..." (Kuro to Mahiru after taking out the trash)
- "Owww! The agony! An apple juice might help! Or a cola..." (to Mahiru)
- "You read too much manga." (to Mahiru)
- "Yes mommy..." (Kuro teasing Mahiru)
- "Me want ramen! Yumm..." (to Mahiru)
- "I follow your sign. If cancer gets bad news, I wanna know. And protect myself!" (to Mahiru)
- "You always give one hundred and ten percent...that's way too much. Sit down." (to Mahiru who kept helping everyone who needed it)
- "And never force him(Mahiru) to do that again." (Kuro threatening the C3 employees after Mahiru had to use a dangerous amount of power to break out, causing Mahiru harm in the process)
- "Where's Mahiru?" (Kuro to the C3 employees, mad that he was apart from Mahiru, putting Mahiru in danger)
- "Housewife." (Kuro teasing Mahiru)
- "Aww...It's okay. I just say, 'He told me to do it.' Free will is overrated." (to one of Berukia about Mahiru)
- "Mahiru...do you trust me?" (to Mahiru)
- "I have...lots...of them. But...I...can't tell you. Some things you shouldn't know. Some things...could kill you." (to Mahiru after he asked if he had anymore secrets)
- "Kuro" (クロ) literally translates into "black", Mahiru named him so due to his black fur when he is in cat form.
- His contract item is a cat bell.
- His favorite food is instant ramen and potato chips (with consommé flavor).
- His favorite drink is cola.
- His favorite ice cream flavor is cookies and cream.
- He dislikes the sound of the alarm clock and the vacuum cleaner.
- His hobbies are playing video games and looking for a comfortable pillow.
- His favorite color is black.
- In official illustrations Kuro is often drawn in both his cat and human form.
- His catch phrases are 「めんどくせー」 (mendokusē) which roughly translates into "what a pain" and 「向き合えねぇ」 (mukiaenē) which roughly translates into "can't face it".
- He hates vanilla ice cream.
- He claims to dislike drinking blood from Mahiru.
- Aside from Mahiru, he likes to give and calls the other Eves with nicknames instead of calling them by their names.
- In his cat form, a lot of girls at Mahiru's school find him adorable and sometimes dress him up in girly outfits.
- Whenever Kuro really has to drink Mahiru's blood, he mostly does it in his cat form and bites him on the arm or leg, never his neck. The only time he drink from his neck is when Kuro lost control during the fight against Sakuya.
- Kuro rarely drinks blood, and when offered, he rejects the idea or makes an excuse, preferring to eat junk food instead; the reason is not yet known.
- In Drama CD, Licht took a liking to Kuro when he first saw him in his cat form. This continues even after knowing he's actually a vampire, affectionally calling him "Neko-san" (Mr. Cat), much to Kuro's dismay.
- He has a patch on his left shoulder with the Roman numeral 1, probably because he is the oldest of the seven deadly sins; Snow Lily also has a patch on his left shoulder with the Roman numeral 7, and on the fifth volume cover Lawless had a patch with the numeral for 5.
- In the first popularity poll he came first with 7145 votes.
- His star-sign is Capricorn.
- In summer, he always wears Mahiru's uncle's pajamas. He initially borrowed Mahiru's, but the difference between their height doesn't fit with Kuro.
- Mahiru thinks that Kuro's strongest point is he always accompanies Mahiru whenever he is eating as Mahiru feels lonely when eating alone, while his weak point and the one thing Mahiru wants to change is Kuro always eats potato chips while playing games because the oil gets all over the place.