Naomasa Tsukauchi/Synopsis

History
Naomasa Tsukauchi is the eldest son of a family. After his little sister Makoto Tsukauchi manifested her Polygraph Quirk for the first time, she kept asking Naomasa sometimes uncomfortable questions, to know if he was telling the truth or not. This bothered Naomasa and asked her sister to stop, although their mother asked him to just humor her.

Years later, he joined the Police Force and became a detective.

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 "Instant Villains" although, many of them were previously defeated by a local vigilante group known as Naruhata Vigilantes. Although they help keep the peace, Naomasa tells his partner Sanza that there is something called the law, and carrying out personal acts of vigilantism is a crime.. The former Instant Villains are interrogated, and 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 of the Instant Villains that was defeated by the Naruhata Vigilantes is Teruo Unagisawa. After interrogate him, they decide to release him, but he is followed by Naomasa. Kuin Hachisuka, one of Trigger's main distributors, uses his Queen Bee Quirk to transform innocent people into a Instant Villains and cause an outbreak. Naomasa immediately calls for backup, and numerous heroes appear and subdue the Instant Villains. The situation is controlled, but Naomasa finds that Teruo has disappeared, having been kidnapped by Kuin for unknown reasons.

Because innocent people have been involved in this incident, 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 Instant Villains continue to happen, as well as their defeats at the hands of the Naruhata Vigilantes.

One night, Shota Aizawa, known as the Hero Eraser Head, defeats one of these "instant villains" who presents a very strange physique (the villain turns to be none other than Teruo Unagisawa, which had been bioengineered). 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. 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 (known as Number 6) 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. Since Pop☆Step was involuntarily involved in the Kanidoge incident, he ends up having an argument with his sister Makoto, who is Pop's manager. Naomasa wants to interrogate her because the incident in addition to her past as a Vigilante, but Makoto protects Kazuho and will not let him treat her like a criminal, assuring him that she has abandoned his life as a Vigilante and now has a legal occupation as an idol.

Along with Tanema, he analyzes 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.

The investigation on the distribution of the trigger and the speedster villain continues. Days later, Naomasa informs Eraser Head about the existence of a new variant of Trigger, that only needs to be ingested to work. This new drug is connected to the instant villains who attended to Mixers, so the police suspect the drug is mixed into the drinks, and the victims are getting roofied. He asks Shota for help, but since he does not like to have to attend parties of any kind, he suggests that Midnight be the one to participate in considering it more appropriate for that kind of mission.

Shota's decision proves to be right, as Midnight manages to find the main responsible for drugging the drinks with Trigger, capturing her and giving her to the police. Midnight is congratulated by Naomasa for the work done.

From the subsequent interrogation and investigation, he learns that the new orally administered Trigger, it's less effective that the regular version but does not turn people into full-blown villains, so it makes it easier for the Villain Factory to distribute it and search potential candidates to kidnap and transform into Next-Level Villains. He also learns that Number 6 is the main responsible for its distribution. The investigation led the police to the place where the deals were happening, but they’d already cleared out. Also, the new trigger came from China, out of Japanese jurisdiction. Naomasa reports to Eraser Head all this new info.

Sky Egg Bombing
Thanks to the information that was given to him by anonymous sources and to an arduous investigation, detective Naomasa manages to locate the place where the Villain Factory carry out its illegal experiments for the creation of the Next-Level Villains with the consumers of Trigger that its agents kidnap. The Villain Factory’s laboratories are located in an isolated area of the Onomura Pharma Corp., a medium-sized pharmaceutical company.

Once determined the place, Naomasa organizes the police forces to carry out a raid. For the operation, they will have the help of the heroes Eraser Head and Fat Gum, in case they have to face serious threats. With everything ready, on the same day that the Captain Celebrity's farewell show is being held at the Tokyo Sky Egg, police forces surround Onomura’s main building and assault it.

The Police Force and the Heroes move quickly through the building until they reach the secret laboratories, arresting all suspicious workers and confiscating all possible evidence in the process. Once in the labs, they meet Number 6, surrounded by creatures known as Bombers. Before the police or the heroes can stop him, Number 6 activates a device that causes several of the Bombers to explode, destroying the labs. The villain manages to escape with five of the Bombers, with the objective of attacking the Tokyo Sky Egg and killing Captain Celebrity.

Fortunately, Naomasa and his allies manage to survive the explosion thanks to Fat Gum, and along with Shota, flies quickly by helicopter to the Tokyo Sky Egg. There Shota uses his Erasure Quirk to help the heroes who are fighting the Bombers, and managing to defeat the creatures. However Shota fears that the enemy has another trick up his sleeve, and asks Naomasa to call All Might for help.The detective is somewhat reluctant to summon the number one hero for a mere precaution, but Aizawa tells him that they are dealing with an unprecedented crisis, with thousand lives at stake, so it's not the time to get carried away by the regulation and normatives.

Naomasa agrees to Aizawa's request and calls All Might. Naomasa tells him that the Tokyo Sky Egg is in trouble, but before he can clarify him the situation, Number 6 succeeded in getting the building to collapse by causing one of the Bombers to self-destruct. Naomasa watches impotently as the building collapses, with thousands of people inside, including his sister Makoto Tsukauchi. Then he desperately asks All Might to save his sister. Thanks to this, All Might arrives in no time to landing the Tokyo Sky Egg dome safely and saving everyone.

Journalists and reporters arrive to report the Bombers' attack on the Tokyo Sky Egg, and ask All Might about his opinion. After his statement, he says goodbye and runs away, being pursued by the media. After elude them, All Might, now as Yagi Toshinori, returns to the place and meets secretly with Naomasa. He tells him that he’s going to stick around for a while in case there’s another attack.

Naomasa apologizes for getting bent out of shape, but Yagi tells him that it’s fine and that it was his impassioned plea that got him there in time. Yagi explains to Naomasa that his Quirk has a strong psychological component to his strength. When he hears a plea for help, he feels it like a direct order to All Might. He tells him that when he accepted his power in order to save everyone and give them hope.

Naomasa feels confused about he "accepted" his power, and All Might realizes that he has unwittingly revealed an important fact regarding One For All and its secrets. Before their conversation continues, they are interrupted by Shota Aizawa, Fat Gum and Monika, and Naomasa introduces them to Yagi, who thinks that one of these days he will have to explain Naomasa everything about the secret behind All Might.

Number 6 does not give up, and attacks again sending a swarm of Mini-bombers, but transformed back into its muscular form, All Might destroys all creatures, being cheered by those present. Then he disappears again to meet Naomasa as Toshinori Yagi.

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 Unforeseen Simulation Joint 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 the 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 there has been an unexpected development; they have probably located the League of Villains hideout. Naomasa plans a rescue operation after this top-secret intelligence has been verified and asks Toshinori to join the operation. The hero thanks Naomasa for his hard work and plans to get payback once he has found the villains.

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.

All Might manages to defeat All For One at the cost of losing the One For All forever. 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.

Endeavor Agency Arc
At the end of December, Nezu talks to All Might and detective Naomasa through a video call. They talk about the fact that since all the students moved into Heights Alliance four months ago, they have been being watched to discover the League’s spy, but in all that time no one has shown signs of being the spy, so it seems that the traitor is not one of them.