Iwao Oguro/Synopsis

History
In the past, Iwao Oguro was a Pro Hero known as O'Clock, while in China he was known as Ciupan Seikyun (Hyper Quadfist). He was a hero specialized in fighting crime, sometimes solo and sometimes working with the Police Force, most often Detective Eizo Tanuma, being responsible for taking down an impressive number of illegal organizations.

The Underground Masquerade
On one of his missions, Iwao disguised himself as a Quirkless knife fighter called The Ripper in order to infiltrate the Underground Masquerade. Inside the fight club, Iwao was pitted against Kendo Rappa, known as The Rapper, who he briefly traded blows with before losing the match by feigning a knockout in order to get sent to the sick bay. Inside the sick bay the doctor offered Iwao an injection containing Trigger and various other stimulants. Iwao used his speed to steal the syringe as evidence and swiftly defeated the guards.

As Iwao exited the sick bay, he ran into The Rapper, who gave him more than half of his winnings from their fight. The Rapper complimented Iwao's fighting ability and offered to have a proper deathmatch someday in the future. Their conversation is interrupted when they heard Rumi Usagiyama, under the persona of Tiger Bunny, crashing the party and causing a commotion in the arena.

While Rumi was fighting everyone in the club, an alarm went off and light-colored gas started pouring out of the overhead pipes. Iwao and Kendo noticed that all the people who inhaled the gas were losing control of their Quirks, and deduced that the gas was a kind of Quirk booster. Iwao also noticed a dark mist appearing near rampaging people and stealing their Quirks. He saw the black gas appear behind Rumi and a hand reach out from it. He quickly scaled the fence she was standing on and carried her away from the black gas, noticing that it was following them. He navigated through the crowd to lose the mist and returned to where Kendo was. Iwao revealed to him and Rumi that he was the High Speed Hero: O'Clock and requested their assistance.

Iwao stole gas masks from some staff and gave them to Rumi and Kendo and briefed them about how they were going to escape. With the mask on, Iwao could only activate Overclock in short bursts, so he instructed the other two to (non-lethally) attack the other people in order to bait out the black mist while he used a gun to shoot the security cameras, which he deduced to be how whoever was controlling the black mist was seeing into the venue.

Kendo noticed a hooded figure and attacked him, but the latter was able to dodge his punches and landed a blow by twisting his arm around Kendo's fist. Seeing The Rapper get thrown back, Rumi attacked the Hooded Man, only to get kneed in the face and sent flying. The Hooded Man stretched his arm to attack Rumi, but Iwao stepped in and used his knife to cut off the stretched arm, shocking Rumi and Kendo. The Hooded Man regrew his arm and angrily recognized Iwao as O'Clock. The Hooded Man launched another enhanced punch, but Iwao used Overclock to dodge it. The giant fist crashed through the wall of the arena, sending patrons running as the cage collapsed.

Iwao instructed Rumi to escape the facility and get the police squad outside to call in All Might as backup. He stared down the Hooded Man, noting that he was performing his attacks with the use of both a regeneration Quirk, and a transformation one, which allowed him to alter the structure of his body to extend and grow his limbs at will. He also noticed that the Hooded Man's style of martial arts was not compatible with the way he used the Quirk, he tended to use powerful attacks with a long wind-up time. Even though Iwao's more calculated fighting style allowed him to counter the attacks, he couldn't overtake the Hooded Man's regeneration due to his mask restricting his breathing. As the Hooded Man noticed Rumi running for the exit, he extended his arm after her in an attempt to grab her, but The Rapper used the distraction to punch him in the face.

Seeing that Rumi was successful in her part, Iwao tells The Rapper that they need to hide, but the latter declines and wants to fight the hooded man, forcing Iwao to stay and fend off the foe until All Might arrives. Iwao notices a hand emerging from the black mist and forcing several attendees to rampage out of control, making a challenge for the Police Force outside.

As Iwao was taking a breather, the Hooded Man knocks out Rapper using a piece of the ring cage. Iwao notes that the Hooded Man is smarter than he appears, and as he is about to swatted by him, Rumi arrives and kicks the Hooded Man down. He and Rapper tell Rumi to leave, but she refuses and stays to fight, impressing Iwao. The Hooded Man gets back up, but is retrieved and taken into the black mist, confusing the three. All Might arrives, but is confused by the sudden disappearance of the villain.

As cleanup outside the parking garage finishes, Rumi prepares to leave. Iwao offers compensation by mentioning her in his report, but she declines, saying that she will make it big on her own as a full-fledged hero. After she hops off, Rapper prepares to head out and fight elsewhere. Iwao tells him to be careful, believing that the Underground Masquerade will start up again under a new name. As he takes off his mask, Rapper says he can't wait, saying he'll be up for any offer to fight with Iwao in the future, and leaves.

The next day, Iwao and Detective Eizo Tanuma investigate the scene of the Masquerade, reminding him that his Quirk is better suited for gathering intel rather than combat, so he lets other heroes take the lead once he's found enough intel. That said, the recent incident prompted him to team up with a pair of accomplices. Eizo asks for more information about the accomplices and the interferences, but Iwao insists on investigating first, taking into account that his opponents are crafty and have access to official channels. Eizo asks if he is being cautious, but Iwao responds that he needs to be prepared for more, before running off again.

The Fall of O'Clock
Iwao and Eizo eventually discover that the one behind the Underground Masquerade was criminal mastermind All For One, as Iwao continued to investigate the villain's whereabouts.

His career as a Pro Hero came to end when he stormed a building, encountering All For One, who promptly stole his Quirk Overclock, leaving his face split open. Iwao survived the encounter, though many left him for dead. The loss of his Quirk and the end of his career caused Iwao to fall into severe depression, beginning to drown his sorrows with alcohol.

Iwao has a daughter, Tamao Oguro, with whom whose relationship became strained after she expressed her desire to become a musician with her friends, only for him to yell at her in protest and tell her to stop hanging out with that group of people. These discussions caused Tamao to leave home at some point.

Following Tamao's sudden departure, Iwao's wife was hospitalized and is currently unable to speak properly. In an effort to track down his missing daughter, the former Pro Hero becomes a vigilante. During his first investigations, he discovers that the body of his daughter has been controlled by a parasitic bee known as Kuin Hachisuka, who works for a mysterious criminal organization (later known as the Villain Factory) that traffic with Trigger, and that seems to be responsible for the vegetative state of his wife.

Since then, Knuckleduster is looking for a way to rescue his daughter, and put an end to the Villain Factory's operations. To carry out his objective, he uses several aliases to hide his identity, as well as to have contacts with both the criminal world and the forces of law to obtain information and supplies.

During his investigations, Iwao met Koichi Haimawari for the first time. Drunk, he was fighting with a thug he considered suspicious to get information about the Trigger when Koichi intervenes to stop them. The thug leaves angrily after hitting Koichi, for not considering that he was the victim of an unprovoked assault by a drunkard. Despite the beating and bleeding from the nose, Koichi offers Iwao some tissues for his injuries. Iwao decides to leave without saying anything to him, barely showing his face, and smiling at the boy's good heart. Koichi's selfless and altruistic behavior prompted Iwao to rethink his current lifestyle and research methods.

Vigilantes Beginnings Arc
Under his vigilante persona of Knuckleduster, Iwao meets again Koichi Haimawari, along with Kazuho Haneyama, while they are assaulted by Soga Kugisaki and his mates Rapt Tokage and Moyuru Tochi, and decides to intervene, defeating them with ease. After that, he examines their tongues to see if they’re discolored, but cannot find anything. However, impressed by Koichi's bravery, Knuckleduster decides to take him as his disciple to make him a hero, even though Koichi doesn't want to be his disciple.

Next morning, despite Koichi's refusal of his offer, Knuckleduster goes to his penthouse. He explains to him and Kazuho the whole issue referred to Trigger, a drug that gives a boost to an individual's Quirk while also weakening their sense of reason, turning them into Instant Villains. He tells them that is characterized by leaving on its consumers’ tongues a characteristic black discoloration, which is what he was checking for on Soga and his friends. Knuckleduster explains that they will beat them, make them talk about the dealer who gave them the drug and cut off the circulation of Trigger. Koichi thinks that Knuckleduster is not being serious.

However, to Koichi's misfortune, Knuckleduster is dead serious, and his method of investigation consists of punch first and ask question later. Pop☆Step arrives and decides to help them by searching on the internet for "sudden villain appearances" which will allow them to pinpoint the location of the Trigger Junkies. In that moment Knuckleduster spots Mario Kugutsu, a salesman who looks suspicious to him, and tries to interrogate him by force.

When he's about to use violence to force Mario to speak, at that moment Shota Aizawa appears and stops Knuckleduster under the suspicion that he is a villain, which causes Knuckleduster and Eraser Head to start fighting, much to Koichi and Pop☆Step's shock. That moment is used by Mario to escape, and Koichi and Pop chase him after realizing that Knuckleduster was right in his suspicions.

It turns out that Mario Kugutsu is a Trigger dealer for the Villain Factory, who has recently supplied samples of Trigger to Soga and his friends, who appear to be taking revenge on Koichi and Knuckleduster for the beating they suffered in their last quarrel. Mario, Soga and the others inject the drug into themselves, causing them to become Instant Villains, and attack Koichi and Pop.

Meanwhile, Shota decides to stop his fight with Knuckleduster as he has realized that Knuckleduster is not a villain after all, just a stubborn Quirkless old man. At that moment, they hear screams caused by the villains' persecution of Koichi and Pop, and they collaborate together to defeat and arrest them. During the battle, Knuckleduster witnesses Koichi's heroic spirit in saving Pop from Mario.

After the battle, Shota thanks him for his assistance but finds his actions to be dangerous. Knuckleduster does not mind helping since he is natural to cooperate with Heroes. He says to Shota that Heroes need people like him since he is free to deliver justice without restrictions. Shota considers his reasoning ridiculous and finds him to be a troublesome old man, although Knuckleduster feels praised for his words and leaves.

Then, Knuckleduster reunites Koichi and Kazuho, and praises the young man for his heroism, telling him that despite his refusals of his offer to make him a hero, he still aspires to be one. Knuckleduster encourages Koichi to chase after his aspiration to be a Hero. Koichi finally accepts Knuckleduster as his master to be trained by him.

Now that he is Koichi's master, Knuckleduster asks him about the speed of his Slide and Glide Quirk. Koichi states that the speed is that of a bicycle and if he goes any faster than that, he will lose control since his Quirk does not have any brakes. Knuckleduster gives Koichi protective gloves that motorcyclists use and suggests him to practice the art of falling safely. Knuckleduster also tells Koichi that he needs a new name, as "Nice Guy" will cause evildoers to make light of him. So Koichi adopts the name of "The Crawler".

During the following weeks, Knuckleduster is dedicated to training Koichi, and patrolling the streets with The Crawler and Pop☆Step to end the traffic of Trigger, which leads him to face several Instant Villains such as Akira Iwako, Teruo Unagisawa and Bat Villain among others.

Their actions interfere in the plans of Kuin Hachisuka and the Villain Factory, responsible for the many incidents in which they are involved. Kuin wants to eliminate them, but the mysterious leader of the organization is more interested in using the Vigilantes to obtain data and blood samples from the Instant Villains.

In one of these missions, Knuckleduster finds some clues about Kuin, but not enough to find out the exact whereabouts of his brainwashed daughter. This leaves Iwao discouraged for a time, though he soon regains his spirits after crushing a few instant villains more.

Stendhal Arc
During a patrol in which Knuckleduster was absent, Koichi meets another vigilante named Stendhal, who saves his life when fighting Akira Iwako. When he returns to his penthouse, Koichi tells his master about what happened, and he stars gushing over Stendhal. Knuckleduster warns him that guys like Stendhal, since those who use "justice" as an excuse to pick fights are nothing but trouble. Koichi acknowledges that he is right about that, although he considers that Knuckleduster is not the most suitable to say something like that taking into account his way of "imparting" justice.

Turns out that Knuckleduster is right in his opinion on Stendhal because, unlike him, he does not hesitate to kill the criminals and anyone who dares stand in his way. He becomes more and more disillusioned with hero society, to the point where he begins to work with Kuin, who was supplying Trigger to several small-time villains.

One of the targeted criminals is Soga, who, after realizing the seriousness of his actions, decides to get away and remove his friends from everything related to Trigger, challenging Kuin in the process. The agent of the Villain Factory forces a fight between him and Stendhal, using a swarm of bees to inject Trigger into Soga by force, transforming him into a Porcupine-like beast to face Stendhal.

While doing his patrol, Koichi hears Soga's screams of rage. When he arrives at the place, Koichi is shocked when he sees Stendhal draw his sword and cut Soga. At that moment, Koichi realizes that Stendhal truly intends on killing Soga, so he risks his life to save the injured Soga from the murderous vigilante, being wounded in the process. Stendhal uses his Bloodcurdle Quirk to paralyze them, but as he prepares to kill them, Knuckleduster intervenes.

Stendhal recognizes Knuckleduster as the "Vigilante of Naruhata" and has no intention of fighting him because he views him as someone who is forging the path of righteousness in this crooked society and as a result they share similar ambitions. However, Knuckleduster does not view himself as being similar to Stendhal as he sees himself as a champion of justice while Stendhal is nothing more than an insane street murderer.

Stendhal is disappointed that he and Knuckleduster cannot reach a mutual understanding, but Knuckleduster knows that Stendhal is disappointed that he lost the chance to launch a surprise attack after noticing Stendhal gauge the distance between them. Then, Knuckleduster lays down a line of wire and tells the killer that he'll punch him if he steps over it. Accepting his challenge, Stendhal charges forward to strike down Knuckleduster, but when he gets close, Knuckleduster steps over the line and slams his fist into Stendhal's mask which sends the killer flying back and badly injuring his face.

Pointing out that he never said that he wouldn't cross the line himself, Knuckleduster picks up Stendhal's broken mask and tells Koichi that people like Stendhal consider themselves more powerful than they really are when they put on a disguise, acting rashly and ignoring common sense. But when they face a real challenge is when they really realize how fragile they are due to their lack of resolve.

After hearing Knuckleduster's statement and despite having his nose broken, Stendhal attacks the Vigilante again and manages to paralyze him with his Quirk. However, instead of finishing him off, a bloody Stendhal thanks Knuckleduster for enlightenment him with his "lack of resolve" speech and leaves the place. Shortly after Kazuho arrives with first aid kits to treat the wounds of Knuckleduster, Koichi and Soga.

Vs. Queen Bee Arc
Thanks to their activities as protectors of Naruhata, Knuckleduster, The Crawler and Pop☆Step begin to be known by the people of the city as the "Naruhata Vigilantes", although there is much misinformation about them. Their fame makes a student from Koichi's college take an interest in them, Makoto Tsukauchi, because she is writing a thesis about vigilantism, and asks Koichi to help her with her investigation.

When Koichi tells Knuckleduster about it, he warns him that Makoto's investigation may cause their identities to be revealed, and the Police Force along with Villains will come attacking in droves. Knuckleduster offers to keep Makoto silent with brute force, to which Koichi promises to deceive her as long as he does not interfere. Knuckleduster decides to let Koichi handle the situation but warns him not to let his working and private lives intertwine. After a series of incidents, Koichi manages to keep their vigilantes identities hidden thanks to a misunderstanding.

Several days later, Knuckleduster shows up at Koichi's house, where he meets Makoto and Shoko Haimawari, Koichi's mother who had come there to visit her son. Koichi and Kazuho start to freak out because they fear the reaction he may cause in Shoko and Makoto when they see the violent vigilante, but fortunately, on that occasion Knuckleduter is not wearing his Vigilante attire, and politely introduces himself to the guests as “Takeshi Kuroiwa”.

"Takeshi" gives Makoto and Shoko his business card, presented a perfect façade of a worker for a local non-profit organization, metaphorically telling them the truth that their organization is dedicated to patrolling and keeping the streets of Naruhata clean.

Makoto and Shoko become friends, and decide the next morning to tour the city forcing Koichi to accompany them. The tour proceeds without incident, but when they are preparing to return, Kuin Hachisuka decides to strike again. She injects Trigger into a cat with a Quirk, making the animal to merge with the bus that Koichi and his companions ride on. The transformed vehicle goes out of control, endangering the lives of passengers and pedestrians.

Knuckleduster notices the ruckus, and when he sees Koichi, Shoko and Mokoto in danger, he decides to take maneuvers to prevent the transformed vehicle to crash. With a makeshift cat toy, he makes the vehicle travel down a fast lane that has a destroyed overpass, but is devoid of people and obstacles, and is long enough, giving enough time for Kocihi and the Team Idaten can rescue everyone before reaching the edge.

During the rescue, he and Kazuho take care of Shoko, while Koichi helped in the operation, rediscovering his ability to jump in midair. Shoko remembers of times when an infant Koichi started using his Quirk for flight even before he could walk. She was so terrified that he would hurt himself that she punished him every time she caught him doing it until he forgot that he could. "Takeshi" mentions there comes a time when every child has to fly in some point of their lives and all they could do is teach them how to fall right. After the incident, Shoko prepares to return to her house, sure that her son is in good hands.

During all these events, Knuckleduster continued with his investigation to find the whereabouts of Kuin to rescue his daughter. At some point, he asked Soga for help. After visiting his wife at the hospital, Soga informs him of his latest clues about Kuin, which allows Iwao to advance his research.

Knuckleduster finally manages to find Kuin when she is about to release Teruo Unagisawa, a Next-Level Villain with the Eel Quirk, at the Narufest event. Koichi and Kazuho also participate along with other artists. Kuin thinks that by occupying the body of his daughter, Tamao, Knuckleduster will not dare to attack her, but she is wrong since Knuckleduster has no qualms about using his new weapon, a Taser Knuckle, against her.

Kuin tries to avoid directly facing Knuckleduster by using all kinds of tricks such as Bomb Bees, but Knuckleduster perseveres. During the fight, he receives a call from the hospital informing him of the worsening health condition of his wife. He responds that soon the whole family will be right over. Once cornered, Kuin does not hesitate to resort to more violent methods. After injecting herself with a sample collected from Teruo (who was defeated by Shota), she temporarily gains electrical powers that she channels through claws on her fingers, and manages to stop Knuckleduster’s heart in one hit.

Thinking that she has killed Knuckleduster, Kuin continues with her plan to crash the Narufest party, but Knuckleduster reappears and reveals that his Taser Knuckle also has a defibrillator function which allowed him to survive. Kuin attacks him again, but this time it is Knuckleduster who defeats her with an electric attack, using the Taser Knuckle.

Due to the Taser Knuckle's shock, Knuckleduster manages to get her swarm to leave his daughter's body by stopping his daughter's heart. He then extracts the queen bee, Kuin, from her eye, and calls back the swarm with a pheromone and bomb combination device, which explodes, killing the queen bee and the swarm.

Knuckleduster manages to resuscitate his daughter and save her, taking her to the hospital where his wife is hospitalized, who unfortunately dies shortly after their arrival.

After defeating Kuin and saving his daughter Tamao, Knuckleduster continues as a vigilante along with Koichi and Kazuo, but for a time there seem to be no more incidents related to Trigger and Villains’ imprisonment, as they’re only defeating simple petty criminals. Koichi thinks that Trigger has stopped circulating in the streets, but Knuckleduster tells him that the people behind those incidents have not surrendered.

He visits his hospitalized daughter, who has been being taken care of by Soga. When Tamao asks for her mother, he simply replies that at that moment she can not see her. Shortly after, Knuckleduster disappears without saying goodbye to Koichi, although he leaves his characteristic Brass Knuckles and his mask in his house.

Sky Egg Arc
After several weeks without hearing anything about him, it seems that Knuckleduster had ceased to be a vigilante after defeating Kuin and saving his daughter, but in reality, he traveled to Hong Kong, where he is still looking for clues about Trigger on his own.

After obtaining the necessary information from some dealers, he returns to Japan to visit his daughter in the hospital, and later, under his alias as Mr. Kuroiwa, he contacts detective Eizo Tanuma to give him information about Japanese importers of Trigger. Apparently, Eizo knows Knuckleduster’s past, and he asks him if he knows anything about a villain who seems to have a similar type of Quirk as O'Clock. Knuckleduster simply says does not know who he's talking about, but advises the detective that if they meet that villain again, do not hesitate to shoot his vitals.

Soon after, he observes Koichi from a distance, happy to see that he continues to fight crime, although he has not contacted him yet.

After this, he continues to perform his duties as a vigilante without telling anyone, investigating the Villain Factory and its movements. Thanks to this, he is aware of their new agent, Number 6, who has been behind the latest incidents related to the Next Level Villains, and who is in possession of his stolen Quirk.

His inquiries and investigations lead him to deduce that the next move of the Villain Factory will be to attack the Tokyo Sky Egg event, to use it as a testing ground. He looks for what would be the ideal rooftop to provide the best view of the Sky Egg in case Number 6 decides to observe the attack, and then search for the ideal spot to snipe him.

As he had deduced, Number 6 attacks the Sky Egg with creatures known as Bombers, with the villain observing everything on a rooftop. Thanks to the intervention of the heroes, his attack fails. Seeing that he had failed and that there is nothing like that he could do, Number 6 is about to leave, but Knuckleduster is not willing to let him.

Aiming him with a sniper rifle, Knuckleduster prepares to press the trigger. Unfortunately, when he is about to shoot him, a bird passes in front of his scope, causing him to miss the shot and piercing Number 6 shoulder. Knuckleduster tries to shoot him again, but the villain quickly locates him, and despite his injury, he jumps from building to building thanks to his Quirk until he ends up on the rooftop where Knuckleduster is.

Number 6 recognizes Knuckleduster as the former hero O'Clock, whom he admires so much. For his part Knuckleduster recognizes him as the villain who is behind all the Next-Level Villains attacks and is also in possession of his former Quirk Overclock, but otherwise, he has no idea who he really is. The villain replies that he is a nobody, a thing still unformed, and he has no real name, he is just called Number 6. However, he confesses to Knuckleduster that he hopes to become O'Clock, since he admires him a lot, and he asks him to recognize him as his successor.

Knuckleduster refuses to grant his request, in fact he does not intend to allow a villain like him, who is in possession of his stolen Quirk, to continue to exist. Number 6 resigns to the fact that his idol recognizes him as a villain, and attacks him. But Knuckleduster knows all the weaknesses and drawbacks of his former Quirk, and uses them against Number 6, causing him to fall into a trap.

Knuckleduster blows up the rooftop and several floors below. Unable to maneuver in the air, Number 6 falls to the bottom, being shot several times by Knuckleduster with a shotgun while falling. Once on the bottom, the vigilante continues to beat him. Knuckleduster admits that killing him was his best long-term option, but now that he had fallen into his trap, it is worth capture him to interrogate him. Knuckleduster tells Number 6 that the building is damaged, and therefore another blast will gonna bring the whole building down, becoming his tomb. He can’t escape even with his super speed.

Number 6 tells him he is naive, because his decision not to kill him gives him the chance to strike back. Number 6 confesses to Knuckleduster that he has bomber cells in his body, as parasites, before self-detonating his left arm, blowing Knuckleduster away. Seriously injured, Number 6 praises Knuckleduster for his stubbornness, considering him as the best hero, even better than All Might himself. However, he is going to surpass him, and be the new O'Clock. Knuckleduster tells him that that will not happen, because in addition to his injuries, he will end him.

Number 6 shows Knuckleduster that, although he doesn't know as much about Overclock as he does, he can do things with the Quirk Knuckleduster could never achieve. Combining overclock with the Bomber's cells of his body, he accelerates the growth of the cells, obtaining an explosive arm where before his left arm was, then, he extends the cells to the right arm, thus obtaining two explosive arms.

Despite all this, Knuckleduster is willing to face him and attacks without contemplation. Admiring Knuckleduster's resolve, Number 6 recognizes that he is certainly the best, before attack him, initiating the final battle between the two.

After the confrontation, only the ruins of the building remain, and the result of the fight or the fate of Knuckleduster is unknown. For weeks, under the command of Detective Eizo Tanuma, the police has been investigated the place, but the only thing they could find were Knuckleduster and Number 6 blood samples. Eizo contemplates the ruins, wondering where Iwao is and what he was up against.

Final Performance Arc
At some point prior to his confrontation with Number 6, Iwao informed Soga to keep an eye out for Koichi and Kazuho, handing him a letter to give to the former if he ever had to go through a great difficulty.

About three years after Knuckleduster left the Naruhata Vigilantes, nothing is known about him since the fight against Number 6, while the villain once again made an act of presence, kidnapping Kazuho and turning her into Bee☆Pop.

Koichi tried to stop her, but he was defeated, being rescued by Soga. When Koichi wakes up at Soga and his friends' apartment, Soga informs him of Knuckleduster's request, delivering the letter to Koichi. Reading the letter, Knuckleduster apologizes to Koichi for not being there to help him, especially since he knows he has taken on one of his problems, while also telling him that he had saved him once long ago, and that Koichi is his hero, reassuring that he knows he will succeed no matter what the situation is.

Naruhata Lockdown Arc
It turns out that Knuckleduster had survived the encounter with Number 6, though suffered damage in the form of a busted knee and a scarred eye. After secretly breaking into Koichi's apartment to reclaim his trademark knuckles, he waits on a rooftop, knowing that Number 6 would attempt to try and trap Koichi, and that he's gotten there first, making his grand return knocking down Number 6 with a flurry of punches before he can shoot.

He continues to pummel Number 6 with an endless array of punches, believing this to be the most reliable tactic to avoid him being able to flee. He taunts him to get him to speak, causing Number 6 to transform his face and start to talk, only to be pummelled some more. Letting him finish his thought, Number 6 screams to Knuckleduster why he chose Koichi and not him, and that all he ever wanted was to become him, pointing his hand to shoot a bullet out of it.

Knuckleduster easily avoids the shot, grabbing onto Number 6’s arm, telling him he picked the wrong guy to idolize, and that even though he was born with a decent Quirk and some brains, that has nothing to do with a man’s true value, and that everything worth it about him that’s left he’s passed on to more deserving people. He gleefully states all he has left to give him is his own worthless life, holding a detonator to his face, as prior to their encounter, he had covered the entire insides of the building they are on in explosives, with the intention of killing them both for good.

To make sure that this time Number 6 can't escape like he did last time, Knuckleduster plans to use explosives that use a different fuel, and that will consume all the oxygen once they blow up, and until that happens, he plans to continue hitting him in the head to not give him the chance to use his quirk.

Number 6 shoots Knuckleduster multiple times with his hand gun, but thanks to his bulletproof vest having minimized the damage, as well taking drugs to keep him on his feet, the vigilante continues punching Number 6 as he starts the countdown. When he reaches zero, Knuckleduster pulses the detonator, but the explosives don't work, much to his confusion.

At that moment appears Soga, telling he had disarmed the bombs once he noticed them. He angrily rebukes Knuckleduster for his suicidal plan, declaring that everyone are putting their lives on the line to make sure no one dies, which means he can't die either.

Number 6 takes this opportunity to flee from the captivity of Knuckleduster and then laughs at him that his elaborate plan to end him has failed in such way. Soga points a gun at him but the villain knows that he doesn’t have the guts to kill someone, while he doesn't have that drawback. Just then, Koichi appears and grabs onto an unsuspecting Number 6, thrusting himself as well as the villain into the sky.

Knuckleduster compliments Soga's plan on using himself as bait, trying to talk and say he's fine, but Soga calls his bluff, telling him to stop talking and that they're going to make sure he doesn't die, since he's still got people counting on him to come home. Knuckleduster looks on surprised as Soga tells him for them to trust Koichi to handle the rest.

As Soga goes for a first aid kit, Knuckleduster watches as Koichi confronts Number 6 in the air. During the battle, Number 6 undergoes various transformations until he becomes a gigantic flaming humaoid, who manages to corner Koichi in a building that he soon knocks down in order to kill him.

Seeing such destruction, Soga shows concern for Koichi but tries to have faith in him, as he prepares to administer first aid to Knuckleduster. Soga orders him to lie down so he can check out his wounds, but the vigilante does not respond. With apprehensiveness, Soga checks that his heart has stopped working.

While "dead", Knuckledusters' "spirit" goes to support his disciple. Under the rubble of the destroyed building, Koichi wakes up surrounded by darkness. Seeing that he is seriously wounded, he thinks that it's going to be the end for him, but then "Knuckleduster" shows up. Seeing him makes Koichi realize that he’s probably about to die, but "Knuckleduster" encourage him not to give up.

Through some suggestions and advice from “his master”, Koichi uses his Slide and Glide to wrap and coat his entire body, overcoming his pain and allowing him to move through the darkness. While searching for a way out, "Knuckleduster" talks with Koichi, telling him how he’s been able to handle everything on his own since he left, while Koichi tells him it’s been rough since then. He praises Koichi’s skills to make ingenuity work.

After a while, Koichi arrives at a dead end. "Knuckleduster" congratulates him for going this far, causing Koichi to believe that he’s reached the end of the line but "Knuckleduster" cuts him off, telling him that now he has go forward encouraging Koichi to defeat the villain using his fists, the same way he does with his trademark brass knuckles. With this advice, Koichi gets the idea of using his Quirk to project force fields on his knuckles, developing the Knuckle Style and punching his way out of the rubble.

Koichi is amazed by the power of his new technique, but precisely because of this he cannot use it against Number 6 because of how dangerous it is, even when the villain does not stop attacking him. "Knuckleduster" shows up again to cheer him up, which surprises Koichi he thought his master reached the afterlife. "Knuckleduster" told Koichi not to worry, and that Number Six’s body is a cluster of pure energy. But they cannot destroy Number Six in a usual way, and they have to do it the old school way. "Knuckleduster" reveals that they have to destroy the core on Number Six’s head.

"Knuckleduster" tells Koichi that Number Six’s body is a cluster of pure energy, but his real body is the skeleton up in the head, and in order to defeat him, he must use his fist and punch Number Six’ remains to knock him dead since, otherwise, he will be killed. The problem is that Koichi doesn't want to kill anyone with his new technique or any other, replying to his master that his idea is not okay.

He’s then surprisingly backed up by an illusion of Pop☆Step, whose appearance caused him to briefly lower his guard, before continuing to evade Number 6's attacks. As they run, "Pop" asks him why he is fighting such a dangerous enemy, Koichi replies that he must keep him there to prevent his rampage from spreading to other areas. "Knuckleduster" says it’s noble, but also that he needs to fight back and scramble his brain, and “Pop” adding without trying to kill.

Koichi is reluctant to use his Knuckle Style against Number 6 because he doesn't want her to hate him, but “Pop” assures him that won't happen. Now that he received the reassurance from "Pop☆Step", Koichi finally strikes Number 6 back with his new technique, piercing his flaming body several times.

This temporarily distracts Koichi, allowing Number 6 to regenerate and attack him, forcing him to escape again as "Knuckleduster" reminds him not to expect the same courtesy from his enemy. As he runs, Koichi replies that in those cases he will just avoid dying somehow. Vigilante and Villain keep on fighting until Number 6 almost manages to kill Koichi with one of his powerful attacks. Although seriously injured, Koichi continues to fight Number 6.

An appearance of All For One, who has always been by Number 6's side, watching everything since his attack on Naruhata began, is impressed by both fighters' serious determination, causing him to wonder what really drives them to take such a massive action. His inner monologue is interrupted when he hears "Knuckleduster" telling him that a scumbag collector such as him would never understand, but when he turns around he sees no one.

Koichi continues fighting Number 6 until finally the Pro heroes arrive, and between All Might and Endeavor they finally manage to defeat the villain. Elsewhere, “Pop☆Step” sings for Number 6, with “Knuckleduster” asking why she isn't singing for Koichi, which she explains is because it's a song about being stubborn and hanging in there, further stating she'd rather talk normally to Koichi than sing to him. "Knuckleduster" tells her that their time is up, and both illusions vanish.

Back on the rooftop, the real Knuckleduster comes back to life thanks to Soga, who used his customized Taser Knuckle to defibrillates him. The exhausted Soga tells Knuckleduster again to doesn't get to die on him and Koichi.