After accepting Koichi Haimawari as his apprentice, Knuckleduster explains him about the drug called Trigger, that significantly boost the user's Quirk while simultaneously weakening their sense of reasoning. Knuckleduster states that they are going on patrol to beat any suspect of being a trigger consumer. Koichi thinks that he is not being serious, but he is when Knuckleduster does indeed start preparing to beat some thugs.
After the thugs leave, Pop☆Step arrives and Koichi tells her the situation. Knuckleduster spots a salesman and starts with him, making the salesman drop his suitcase which has Hero figures. Knuckleduster finds the salesman to be suspicious, but Pop☆Step and Koichi try to stop him. Before Knuckleduster make him spill the beans, his arm is wrapped by Aizawa’s Capturing Weapon. Thinking that he was part of the "spontaneous villain" outbreak, Shota tries to stop Knuckleduster, but he responds violently, starting a fight between the two, much to Koichi and Pop☆Step's shock.
With his arm still wrapped by Aizawa's cloth, Knuckleduster attacks him, but Shota dodges the blow and kicks him in the face. Knuckleduster does not take any serious damage from Shota's kick and prepares to attack back. Grabbing the piece of cloth, Knuckleduster throws Aizawa through the air, although he lands on a tree without suffering any damage. Believing that Knuckleduster possess some kind of stamina enhancing Quirk, Shota activates his Erasure.
While Knuckleduster and Shota continue fighting, Koichi apologizes to the salesman and asks him to declare his and Pop☆Step's innocence to the pro Hero. However, the salesman leaves in a hurry. Pop☆Step realizes that she has seen the salesman before. Seeing some pictures, Pop☆Step discovers that he has been present in several villain disturbances. She tells Koichi to run after the salesman because he is suspicious.
Meanwhile Knuckleduster and Eraser Head continue their fight. Shota manages to knock down Knuckleduster, but is surprised that it does not seem that the old man has not lost any strength and continues to fight back, despite the fact that Shota has activated his Quirk on Knuckleduster. After being pushed back by Knuckleduster, Shota realizes that Knuckleduster is actually Quirkless.
Understanding this, Shota stops fighting Knuckleduster and apologizes him because if he isn't using a Quirk for illegal activities, then he falls outside hero jurisdiction. Knuckleduster takes Shota's apology and they go their separate ways.
Despite realized that Knuckleduster is not a villain, Shota still believes that he is a suspicious character. Just in case, he's going to file a report on Knuckleduster to the Police Force to take care of him. But at that moment, they hears screams.
The suspicious salesman, along with Soga and his friends, become Impromptu Villain, attacking Koichi and Pop ☆ Step. Knuckleduster and Shota Aizawa decides to work together to stop them.