Koichi Haimawari & Knuckleduster vs. Soga Kugizaki, Moyuru Tochi & Raputo Tokage is a battle between Koichi Haimawari, and the vigilante Knuckleduster against the thugs Soga Kugizaki, Moyuru Tochi and Raputo Tokage.
Before this fight happened, Koichi had already had problems with Soga and his mates Moyuru and Raputo previously. That morning, he accidentally spilled the juice of Soga, and he wanted to humiliate him for it, so Koichi decided to running away. Later, they encountered him again in the convenience store where Koichi works. Soga beat him up and forced him to buy him a new juice before leave. Koichi decided to deliver justice on his own accord without being bogged down by the law. He put his "suit", an All Might-styled hoodie and a mouth mask, and started doing good deeds for the public.With his good deeds done for the day, Koichi begins walking home, meeting Pop☆Step in a alley, an idol that he helped that morning warning her about the police. She thanks him for that but she make fun of him for being weak and wearing an All Might hoodie, which causes both to start arguing. Pop☆Step begins to leave but bumps into Soga and his friends. The thugs recognize her as the online idol, begin mocking her and even thinking to sexually assault her.
At first, Koichi asks them to stop, but the thugs, who do not recognize him because of his "disguise", ignore him. When he insists again, Soga deliver him a death glare. Scared, he decides to leave Pop☆Step to his fate. However, when he sees her scared face, he decides to help her without thinking. Koichi theoretically wonders how he can handle the situation; use his Slide and Glide to trip two of the thugs and take out the leader by tackling him so that Pop☆Step can fly away.
Koichi decides to put his plan into motion and slides into Moyuru Touchi, trying to trip the thug, but fails. Moyuru throws Koichi to the ground. Soga turn their attention to Koichi and recognize him as the “annoying guy” from before. Soga attacks him and scratches Haimawari's face with spikes from his foot. Soga decides to finish off Koichi for annoying him and to strip down Pop☆Step.
Koichi is totally terrified and Pop Step screams for help, but the thugs tease them saying that no one hero will come to help them. Suddenly, when Soga is gonna to attack Koichi again, someone crashes down onto the trash heap.The person gets up revealing to be a muscular old man. Soga ask him what is is deal, but the old man just punches him in the face, knocks Soga down to the ground, surprising everyone. Moyuru and Raputo are shocked at what happened and ask for the old man's motivations. The old man tells them that he is Knuckleduster, a “cleaner” specializes in dealing with hoodlums like them.
Knuckleduster suddenly asks Raputo if he has drugs in his possession and orders him to show his tongue. Before he can answer, Knuckleduster punches him hard in the stomach and sticks his tongue out, checking that it does not have any discoloration. After finishing him, he easily defeats Moyuru and verifies that his tongue is not discolored either.Knuckleduster turns his attention to Koichi and praises him for his efforts, telling him that he can become a real Hero if he works with him. Koichi shows no interest, but Knuckleduster can see through his lies and knows he is someone who cannot abandon people in need like All Might. Koichi admits that his Quirk is not useful and could never pass the Pro Hero Exam. Knuckleduster does not care about whether Koichi has a powerful Quirk or license because they have absolutely nothing to do with justice. Knuckleduster believes that true Heroes take action when something rises up before them. Koichi realizes that Knuckleduster is unlicensed.
Suddenly, Soga gets up and takes Pop☆Step hostage, and threatens to claw her face off with his spikes. Unable to let him get away with his atrocious act, Koichi charges at Soga and knocks him down, allowing Pop☆Step to fly above for safety. Knuckleduster take advantage of the situation and punches Soga into the wall, knocking him out. Knuckleduster sees that Soga is not in possession of the drug he is looking for or that his tongue is discolored. But to make sure, he takes his ID to make a copy.
After defeating the thugs, Knuckleduster talks to Koichi. He informs him that there are more ways to be a Hero than what the world says; Knuckleduster is a Hero because punishing evildoers is refreshing, decides to adopt Koichi as his disciple. However, Koichi finds Knuckleduster to be dangerous and is not sure about joining him.
Later on, the thugs walk in an alley and are badly injured. Soga is annoyed and angry, promising to kill Koichi and Knuckleduster next time, although Moyuru suggests not to get involved with them. Out of nowhere, a man in a suit appears before the thugs and offers them splendid medicines.