Sir Nighteye begins to investigate a Yakuza organization known as Shie Hassaikai, after an incident involving the yakuza's run-in with with a gang of robbers known as Team Reservoir Dogs. However, the Police Force labelled it as an accident which the Nighteye Office found strange since it didn't make any sense and decided to investigate the Shie Hassaikai. A few days later, Bubble Girl reports to Sir Nighteye regarding the meeting between the Shie Hassaikai and the League of Villains that ends in a struggle between them.
Sir interrupts her and claims there is no room for a society without humor. Bubble Girl realize she fails to amuse Nighteye upon supplying him new information and asks him nervously to stop… At that moment, Izuku and Mirio arrive at Nighteye's office, only to find that Nighteye has placed Bubble Girl in a tickle device as punishment for her lack of humor in her report.
While Bubble Girl is released from the machine by Mirio, Nighteye challenges Deku to pass a test after failing to try to make him laugh if he wants to work in his agency. Nighteye orders Mirio and Bubble Girl to leave. After walking out, Bubble Girl asks Mirio if he needed a practical interview like Izuku, to which Mirio replies that Nighteye nominated him so he did not need one. Later Mirio and Bubble Girl renter the rooms, of which Sir Nighteye reveals he will take in Izuku.
Izuku is informed in the operation in which Nighteye is working, and the next day he goes on patrol with Mirio. Meanwhile, Bubble Girl accompanies Nighteye to watch the Shie Hassaikai Compound. After several minutes, Bubble Girl receives a call where Mirio tells them they made contact with Kai Chisaki, leader f the Yakuza. The four meet and Mirio and Deku tell them what happened and that Overrhaul has a daughter named Eri. For their part, Nighteye and Bubble Girl explain in more detail the reasons why they investigate Shie Hassaikai and his mysterious leader before return to the agency.
A few days later, at Sir Nighteye's Office, several heroes gather for a meeting about the Yakuza. The meeting begins with Bubble Girl explaining that the Heroes at Nighteye Office have been investigating the villain organization called the Shie Hassaikai. Centipeder explains that he made follow up investigations regarding the Shie Hassaikai and found out that they have been contacting other villainous groups and involvement with black market groups all over Japan; their motive for doing so is to increase their organization and finance. Soon after the official investigation began, the Shie Hassaikai made contact with a member of the League of Villains called Twice.
Centipeder and Bubble Girl continue with their explanation. Due to their investigation revealing these developments, Bubble Girl states that they requested their help through the Hero Network. As Centipeder tells her to skip that part, Sir Nighteye explains to his fellow heroes the situation. Shie Hassaikai has created a drug capable of eliminating Quirks, using the blood of a girl named Eri. For this reason, he has organized an operation with which to dismantle the criminal organization, arrest its members and rescue the girl.
After several days, Bubble Girl joins the heroes in their mission to arrest the Yakuza members and rescue Eri. Inside the Shie Hassaikai's headquarters near the entrance to the underground labyrinth, Bubble Girl and Centipeder have defeated and rounded up the unnamed Yakuza thugs.
One of the thugs mentions that the Heroes should have cooperated, to which Bubble Girl replies that he is crazy for thinking that, another thug responds that they are all quite sane and if they had cooperated with the Heroes, Overhaul would have killed them in an instant. Bubble Girl remarks that they are referring to Kai. One of the thugs mentions that Kai started using the name "Overhaul" after he fell and became like that. They state that their boss was once a noble Yakuza, looking for a way for the Yakuza to live in today's world and he resented the fact that the Shie Hassaikai have been designated as a villain organization rather than Yakuza.
They mention that they were all devoted to the boss, but their new boss who had given himself a villain name and started taking in actual villains into their group, fear that this may be the beginning of the end. Bubble Girl assumes that Kai is quite hated and asks if they didn't think he'd be caught, to which the thugs agree and mention that the ones who don't think about or care about the consequences are strong.