Naomasa Tsukauchi/Synopsis

Villain Out-Break Incidents
Led by his partner Tanema, Naomasa is part of the investigation into the “Villain Out-Break Incidents" in Naruhata over the past few weeks. All these incidents are related to the use of the drug called Trigger, that boost an individual's Quirk, but turned into a villain instantly.

The police managed to arrest several of these "Impromptu Villains" although, many of them were previously defeated by a local vigilante group. In their interrogations, each of them have been confirmed to use the drug moments before their attacks, and that they acquired it from a stranger who gave it to them without demanding anything in return.

Tanema, believes that since Trigger has been distributed in specific places they could track down the dealers, however is confused as to why the dealers would hand Trigger out for free, considering that it is a very valuable product. Naomasa ponders about the objective the dealers want to achieve. Tanema notes that "objective" is the keyword and surmises that the dealers may want to make massive profit or an upheaval of public order, although he may be overthinking this.

One day, Tanema sent Tsukauchi to request All Might's help in dealing with the Trigger outbreak, specifically telling him to talk to his secretary-manager, Toshinori Yagi, if All Might wasn't available. Naomasa goes to the Might Tower and meets Mr. Yagi, not knowing that he is actually All Might in his base form.

While they are having a conversation in a café, Toshinori constantly makes excuses and run to perform quick deeds as All Might. When Toshinori accidentally returns with the uniform still visible (revealing his dual identity as All Might), Naomasa calls him out on not filing reports on all of his heroic activities, as customary of a Professional Hero. Taking pity on the number 1 Hero, Naomasa offers to file the reports himself, letting All Might act without any worries apart from telling Naomasa what he is doing.

During the following days, the incidents with the Impron Villains continue to happen, as well as their defeats at the hands of the Naruhata Vigilantes.

One night, the Hero Eraser Head defeats one of these "instant villains", Teruo Unagisawa, who presents a very strange physique. Naomasa Tsukauchi approaches Eraser Head to interrogate him about the instant villain situation. Eraser tells Tsukauchi that he doesn't think Teruo is an instant villain, and did not see any injector on him.

Days later, Naomasa has a conversation with Eraser Head and the Midnight heroine. He talks about the new villains that had begun appearing throughout the city. He tells them that Teruo Unagisawa had been arrested twice for being an "Instant Villain", however he had undergone a drastic change between his first and second arrests in that his physical form had completely changed and it seemed to be at least semi -permanent.

In addition, the police had found several other villains with similar alterations that had concentrations of Trigger present in them which was several grades higher than the lethal dose of the drug. This had led the Police Force to suspect that someone had purposefully altered their bodies to withstand higher doses of Trigger.

Naomasa tells Shota and Midnight that he believes there is an organization behind the distribution of Trigger that is also administering to others and altering them to be able to withstand greater amounts of the drug. For the time being, the police calls this organization the Villain Factory.

Shota says that the organization must have some greater goal in mind because by themselves their "Instant Villains" and "Next-level Villains" could not do much and were more like disposable pawns. Naomasa agrees and says that is why he had come, to ask for Shota's help in the matter.

The Speedster Villain
Naomasa's investigations on Trigger's traffic take him to Osaka, specifically to the SS Mall in Super Minami, a shopping/dining district. Apparently, the police suspect that the Villain Factory uses Kanidoge chain, specialized in crab food, to import and distribute the drug. For this operation, they have an infiltrated agent, Monika Kaniyashiki, as a worker in the Kanidoge chain; and Fat Gum in case of needing a Hero for the operation.

When carrying out her research work, Monika goes to the loading docks and analyzes a batch of Kanidoge products. When opening a box, she sees that there are only crab and icepacks in two different sizes, nothing out of the ordinary, which is lampshade by one of the loading docks workers.However, Monika points a gun at him asking who he is. The suspect says he is only a part-time worker, but Monika tells her that she knows each and every one of part-timers who work there. She also realizes that the drug is hidden in the icepacks of the product, and she gets a tablet that contains important information about smuggling operations.

Having been discovered, the suspect uses his Quirk, which gives him enormous speed, to snatch Monika's pistol and tablet. She quickly asks for reinforcements, so Naomasa, Fat Gum and the rest of the police forces come to the place to catch the suspect.

Monika warns Naomasa to be careful as the villain has a acceleration Quirk that gives him extreme speed. When seen surrounded, the villain activates a code that causes that several of the mechs employed by the workers are out of control and go on a rampage. Thanks to Fat Gum and Monika, the workers are rescued and the mechs are neutralized, however, they explode destroying all the evidence. The villain takes advantage of the confusion to flee with the remaining evidence using his Quirk.

While Fat Gum and Monika leave to deal with a Mech that is still active, Naomasa and the remaining Police Force chase the suspect. Naomasa manages to hit him in the leg with a shot, deducting that his Acceleration Quirk needs a cool down time after using it.

Confronted by the police, the Villain uses his Quirk again. In a blink of an eye, he disarms a whole group of cops and shoot in their bulletproof vests with their own weapons. Although this does not kill them, it does leave the police very badly wounded. The Villain being able to finally escape with the tests without any problem.

Naomasa ends up with several fractures and the arm in a sling, but still continues with the investigation of the Villain Factory, the illegal distribution of Trigger, and the appearance of the Next-Level Villains.

Along with Tanema, He analices a security cam tape about the failed attempt to arrest the speedster villain in Osaka. Tanema suggests that he may be one of those people who are so fast that for them the rest of the world seems like frozen in time. This gives Naomasa the idea of meeting with Shota, who tells him about O'Clock, a speedster-type hero of the previous generation who suddenly disappeared without a trace. O'Clock had a very similar Quirk to the Villain’s, and everything seems to indicate that there is some connection between them.

U.S.J. Arc
Outside U.A. High School, Naomasa checks the status of Class 1-A and determines that everyone (except Izuku Midoriya) is unharmed. He then tells Class 1-A to head back to their class. Tsuyu Asui asks him the condition of Shota Aizawa, to which he replies that he is in a critical state but not life-threatening and says that although Thirteen and All Might are injured, they are not in a critical state and are being treated by Chiyo Shuzenji. Naomasa then asks Nezu whether he can investigate U.A., which the principal allows.

Naomasa then visits U.A.'s Nurse Office, friendly greeting All Might. All Might asks him about the status of the students as well as Thirteen and Shota, to which Naomasa states that the students are fine and the teachers are not in life-threatening danger. He then says that if he, Thirteen and Shota had not fought the villains, the kids would probably be in a terrible condition, but All Might says that the students also fought bravely and made those villains look like fools and concludes that they will make fine heroes which Naomasa smiles to.

U.A. Sports Festival Arc
In a meeting with U.A.'s staff, Naomasa tells them that he has investigated the villains Tomura Shigaraki and Kurogiri but could not find any information about them. He then says that they captured and arrested 72 villains at the USJ and says that they were all third rate thugs, however, the problem was that all of them seemingly swore allegiance to Tomura. Naomasa insinuates that in an age filled to the brim with heroes, villains must have felt pressurized and that is why they decided to follow Tomura's "innocent" simple-minded brand of evil. Naomasa says that he is going to assist in enlarging the police force so that they can continue capturing more criminals.

Vs. Hero Killer Arc
Naomasa meets with All Might at U.A. He tells All Might that the Police Force have tried everything to get information out of Nomu, however, everything they tried did not work. Naomasa says that they instead looked into Nomu's background through DNA analysis and have discovered that Nomu was once a human with a criminal record. Naomasa explains that the DNA analysis also revealed that Nomu has the DNA of at least four different humans mixed with his own. Naomasa concludes that Nomu is an artificial human made to measure up to multiple Quirks and that having all the DNA in his body as well as his body modified caused Nomu's brain activity to stop. Naomasa tells All Might the real issue is that Nomu's DNA is of primary concern because it contains multiple Quirks. Naomasa says that Nomu could not have acquired multiple Quirks in any way (unless Nomu acquired the Quirks through advanced genetic familial permeation). Naomasa comes to the conclusion that someone with a Quirk that can grant Quirks is behind Nomu's acquisition of multiple Quirks, much to All Might's horror.

Forest Training Camp Arc
After the incident at Kiyashi Ward Shopping Mall. Naomasa arrives at the scene and takes Izuku to the Police Station to be questioned by him about the event that transpired. At the Police Station, Naomasa questions Izuku about Tomura and their conversation. Although the information Izuku provides is nothing new, Naomasa thanks Izuku for the information and praises Izuku for being level headed during his confrontation with Tomura; The Police investigator is glad with Izuku's actions because collateral damage was kept to a minimum and no lives were lost.

Outside the Police Station, All Might greets Izuku and Naomasa; he apologizes to Izuku for not being there. After All Might answers Izuku's question and Izuku along with his mother leave, Naomasa theorizes that Tomura will probably target other students and decides that Hero schools must exercise more caution and become more proactive in implementing counter measures against villains. Naomasa advises All Might that leaving U.A. is also an option, but All Might decides against it. Naomasa concludes their conversation by saying that they will capture All For One this time, to which All Might agrees.

Hideout Raid Arc
One day after Katsuki Bakugo is captured by the League of Villains' Vanguard Action Squad, Naomasa phones All Might to inform him that they have tracked down the League of Villains' hideout.

A day later at night, Naomasa along with the Police Force and a large number of Pro Heroes wait near the League of Villains' hideout. Naomasa reminds the Pro Heroes of the importance of the rescue operation, that the Hero Society may fall if they do not succeed. Naomasa states that they know the hideout Katsuki is in and tells the Pro Hero team that while investing their efforts in rescuing Katsuki, they will capture the other hideouts to block off the League of Villains’ escape route and then apprehend the villains themselves.

The time for the pro heroes and the Police Force to initiate the rescue operation has come; Naomasa tells everyone that the rescue operation is a battle of speed and to not let any villains retaliate. Naomasa reveals that U.A.'s public apology broadcast was to deceive the villains into thinking that the heroes were having a hard time and could not afford to attack today; thus the pro heroes and the Police Force have the element of surprise on their side for their counter attack since the League of Villains are not expecting them to attack now. The pro heroes and the Police Force head out and stand in front of the League of Villains' hideout, preparing to storm the place.

The pro heroes storm the League of Villains hideout and apprehend Tomura and his fellow villains while another group of pro heroes infiltrate and take control of the League of Villains' warehouse. However, All For One intervenes and summons multiple Nomu while Tomura and his fellow villains escape. Naomasa and the pro heroes deal with the Noumus while All Might goes to chase after All For One. Eventually, they manage to apprehend all Nomus.

After All Might defeats All For One, Naomasa and Gran Torino visit All Might in hospital. All Might who is bandaged and recovering states that he can no longer use One For All and that although he can no longer be the Symbol of Peace, he still has things to do. Naomasa is in disbelief that Tomura Shigaraki is Nana Shimura's grandson. On that topic, Gran Torino comments that Nana Shimura and her husband had a child. However, after her husband died due to heroics, Nana sent her son to a foster family so that he can stay away from the world of heroics. Nana then informed Gran Torino and All Might to not get involved with her son.

All Might wishes to find Tomura, however, Gran Torino tells All Might that he is in no position to help Tomura since he has would not be able to see Tomura as a villain. Gran Torino and Naomasa decide that they will handle the search for Tomura. Gran Torino suggests to All Might that he must remain at U.A and carry out what he must still do; helping his successor, Izuku Midoriya.

Shie Hassaikai Arc
Thanks to the investigations of the police, Naomasa Tsukauchi and Gran Torino have managed to track down and find Kurogiri with the help of eyewitness reports and have subdued him. Gran Torino tells Kurogiri that if they arrest him, the League of Villains will fall apart. As Naomasa warns Gran Torino about Kurogiri's Quirk, Kurogiri asks Gran Torino if he knows of the rumors about a "ruffian" appearing on the mountain where they are at and the reason he is here is to speak to the "ruffian".

Gran Torino would prefer Kurogiri to tell him all about it behind bars. Suddenly, a huge noise reverberates in the area which catches Gran Torino's attention. An enormous beast that towers over trees appears with a boombox around his neck, which surprises Gran Torino. Kurogiri states that the ruffian is one of All For One's faithful servants: Gigantomachia.

He and Tsukauchi are seriously injured and the task force suffer severe casualties at the hands of Gigantomachia, but they manage to took Kurogiri into police custody, at the cost of allowing Gigantomachia to escape, after having completely destroyed a large portion of the mountain. Later, Gran Torino phone All Might to inform him about all of this.