Iwao Oguro/Synopsis

History
In the past, Knuckleduster was a Pro Hero known as O'Clock. During his time as a hero, he took on a pupil. In China he was known as Ciupan Seikyun (Hyper Quadfist). His career as a Pro Hero came to end after his Quirk was stolen from him, his face was split open and he was presumed dead.

After an unknown amount of time passed following the incident, his relationship with his daughter, Tamao Oguro, becomes strained after she expresses her desire to become a musician with her friends, only for him to yell at her in protest and told her to stop hanging out with that group of people. This caused her to leave home.

Following Tamao's sudden departure, Knuckleduster's wife is 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 controled by a parasitic bee known as Kuin Hachisuka, who works for an organization known as the Villain Factory, the same organization responsible for the vegetative state of his wife.

The Formation of the Naruhata Vigilantes
Knuckleduster meets Koichi Haimawari and Kazuho Haneyama for the first time while performing vigilante tasks - looking for consumers of Trigger. He sees Koichi and Kazuho confronting Soga Kugizaki and his mates Raputo 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, despite not having the license.

During the following weeks, Knuckleduster usually visits Koichi at home to train him. He also explains to Koichi and Kazuho the whole issue referred to Trigger, a drug, he eludicates, that gives a boost to an individual's Quirk while also weakening their sense of reason. 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.

During this period, they also carry out several acts of vigilantism, where they face several Impromptu Villains, as well as other minor criminals and oddities. In one of these missions, Knuckleduster tries to catch Mario Kugutsu, a Trigger dealer for the Villain Factory, who has recently supplied samples of Trigger to Soga and his friends. They then inject the drug into themselves, causing them to become Impromptu Villains and try to take revenge on Koichi for the beating they suffered in their last quarrel. He also meets and confronts Shota Aizawa, who later decides to help him to stop and arrest Mario, Soga, Raputo and Moyuru.

In one of these missions, he finds clues about Kuin.

Later, he will face Sthendal, another vigilante who, unlike him, does not hesitate to kill the criminals and anyone who dares stand in his way. Initially, Sthendal worked with the vigilantes such as Knuckleduster, The Crawler, and Pop☆Step. However, he became more and more disillusioned with hero society to the point where he began to work with a Kuin Hachisuka, who was supplying Trigger to several small-time criminals. One of these goals is Souga, who after realizes the error of his actions, decides to get away and remove his friends from everything related to Trigger, challenging Kuin in the process.

Sthendal intends to kill him, as well as Koichi, who risked his life trying to save Soga. Sthendal uses his Quirk to paralyze them, and when he is ready to kill them, Knuckleduster intervenes. During the fight, he lays down a line of wire and tells the killer that he'll punch him if he steps over it. When Stendhal gets close, Knuckle Duster steps over the line and lays him out flat, pointing out that he never said that he wouldn't cross the line himself. Stendhal's nose was completely smashed in and he was forced to retreat, causing minor injuries on the Vigilante. However, his defeat was not a complete loss, as became enlightened after hearing Knuckleduster's comments on resolve.

Afther this, Knuckleduster continues with his investigation to find the whereabouts of Kuin Hachisuka, this time with the help of Soga, who is looking for clues for him.

Narufest Incident
He finally manages to find her when he was about to release Teruo Unagisawa, a Next-Level Villains with a Electric Eel Quirk, at the Narufest event, where Koichi and Kazuho participated, as well as other artists. Kuin thinks that by occupying the body of his daughter Tamao Oguro, Knuckleduster will not dare to attack her, but she is wrong, since Knuckleduster has no qualms about using his new weapon against her, a Taser Knuckle.

Kuin Hachisuka tries to avoid facing directly Knuckleduster using all kinds of tricks, such as bees bombs, 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. When being cornered, Kuin does not hesitate to resort to more violent methods. After injecting herself with a sample collected from Teruo Unagisawa (who was defeated by Shota Aizawa), she temporarily gains electrical powers that she channels through claws on her fingers, and manages to stop Knuckle Duster's heart in one hit.

Thinking that he has killed Knuckleduster, Kuin continues with his plan to crash the Narufest party, but Knuckleduster reappears and reveals that his Taser Knuckle also has a defibrillator fuction, 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. 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 & 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.

A Vigilante's Farewell
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 the Trigger and Villans imprisonment, defeating simple petty criminals. Koichi thinks that the 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 had been 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, Knuckeduster disappears without saying goodbye to Koichi, although he leaves his characteristic Brass knuckles and his mask in his house.