Sansa Tamakawa/Synopsis

Vigilantes Beginnings Arc
Sansa accompanies detective Naomasa Tsukauchi to investigate a place in Naruhata, where a villain had recently been defeated, arriving just as the authorities are about to take him to the hospital. When the detective asks Sansa who the suspect is, he tells him that he is not registered in the Villain compendium so he is looking for his identity in the Quirks registry, although according to the local police, his Quirk is a combination of hardening, superstrength and a bit of of gigantification.

Naomasa then notes that suspect's tongue is black, a side affect of Ideo Trigger, which makes him realize that he is an Instant Villain, and seeing his injuries, he asks his assistant if it is known who defeated the villain. Sansa states that eyewitnesses saw a couple of heroes fighting him, but there are no reports of Heroes being dispatched to the area, so Naomasa concludes that the people responsible are Vigilantes. Sansa is glad that the Vigilantes took down the villain since it works in their favor,, but Naomasa rebukes his words, reminding him that carrying out personal acts of vigilantism is a crime.

Several days later, a meeting is organized at the police station to discuss the latest incidents related to the Instan Villains with various heroes. Shortly after the meeting, a random man breaks in and plans to blow up the building with everyone inside, but he is quickly defeated by the heroes. Naomasa and Sansa walk over to make sure everyone is okay before the villain is put behind bars.

Sky Egg Arc
The incidents with the Instant Villains follow one another, and the police continue to investigate those responsible for them, whom they call the Villain Factory. The police investigation leads to an event in Osaka, where they meet Number 6, a Factory agent who leaves Naomasa and several policemen injured and destroys the evidence.

While recovering from her injuries, Naomasa has an argument with her sister Makoto that ends up causing him to take a bath with bath salts. The next day, Sansa notices how good he smells, and Ezio asks if he has found a lady friend. Naomasa just replies them to leave him alone.

The three end up checking the surveillance footage from the day of the incident in Osaka, analyzing how Number 6 managed to defeat an entire police squad and escape in mere seconds. Eizo suggests that, having an acceleration Quirk, moving so fast that for them the rest of the world seems like frozen in time, and Sansa says it's like he's got heightened focus, and that there are heroes who can deal with shots with their bare hands. Those explanations give Naomasa the idea to research about O'Clock, an old-school hero with similar powers to the villain.

Weeks later, Number 6 uses creatures known as Bombers to attack the Tokyo Sky Egg and kill the CC, but the plan fails thanks to the heroes' intervention. As he prepares to leave, the villain is attacked by the vigilante Knuckleduster, and the confrontation results in the destruction of the building they are in.

While the police investigated the ruins, they found the blood samples of two individuals. After analyzing them, Sansa accompanies Naomasa to inform Ezio that one of the blood samples corresponds to the former hero O’Clock, while the results of the second sample came back inconclusive due to the large amount of chemicals found in it.

Final Performance Arc
A few years pass and Number 6 strikes again, this time kidnapping Kazuho to be Queen Bee's new host, turning her into Bee☆Pop, and uses her to attack Naruhata, causing much damage before retreating. Sansa overhears Naomasa arguing with her sister Makoto over the phone, due Kazuho has been registered as a villain.

A week later, Number 6 and Bee Pop attack again, but this time Koichi and his allies are able to stop her and take her to a hospital, where the parasitic bee is removed. For his part, Number 6 ended up accidentally burned by Endeavor's flames, although he manages to survive and swears to Koichi that he will kill him and Kazuho.

Koichi's allies -Soga, Moyuru and Rapt- are interrogated by Naomasa about Koichi's whereabouts, with Sansa taking notes of their statements, but neither Moyuru nor Rapt say anything clear, and Soga tells the detective that he is wasting his time looking for Koichi, when what he should do is protect Kazuho from Number 6. His answer makes Naomasa run out of patience, which surprises Sansa. Finally, Detective Aonuma allows the three to leave.

Underground Masquerade Arc
At Eizo's request, Sansa digs about the history of the hospital where Kazuho is admitted. After several days of investigating, in the police station office, he informs the detective that the hospital had been receiving generous donations for years, from a man named "Takeshi Kuroiwa" who holds several positions on several companies and non-profits, but there aren't many public details about him. Eizo thanks him for the information.

Sansa notices the envelope Eizo is bringing with him and asks what it is about. The detective replies that it's about an old case and that there is something he wanted to check, though he doesn't tell him of his suspicions that it might be connected to the events of the last few days.

After several hours working, Sansa decides to go for a coffee refill, and Eizo asks her to bring another one for him. When Sansa returned with the coffee cups, a tremendous explosion is heard coming from where Eizo is. Turns out, while he was away, the detective finished reading over the report, realizing that there really is a connection. Disguised as a policeman and taking advantage of Sansa's absence, Number 6 enters the office and destroys the documents and blows up the floor of the building before Eizo can react.

Next day, Naomasa and Sansa investigate the bombing of the police office, with Naomasa wondering what they were after if they went this far to harm its lead investigator. He asks Sansa what Eizo Tanuma was working on, explaining he was digging up the old files related to Naruhata, Osaka, etc. Naomasa laments over the files having been burned up alongside everything, but Sansa states since he was in the middle of editing them and Eizo's notes, they're still on the server.

Naomasa reads the files and states his readings feel like a conspiracy theory, thinking about what their next move should be when Sansa appears telling him the Heroes have just arrived for their upcoming joint operation.

Naruhata Lockdown Arc
Everyone at the police station is alert and very stressed by the recent attack, and none other than Detective Naomasa, who is so focused on recent events that he didn't notice officer Sansa's presence when he shows up. Sansa notifies him that he has the arrest warrant for Koichi Haimawari, who is known as The Crawler. As he thinks that the authority doesn’t have to rely on outlaws, Naomasa tells Sansa that it is their time to make a move. Sansa and Naomasa head out to complete their mission and prepare to retrieve the reins from the Naruhata Vigilantes.

The two of them, along with Midnight and a police squad, return to the hospital where Kazuho is admitted, and confront Soga and his buddies, ordering them to let the police take care of security, and informing them that there is a arrest warrant for Koichi. Soga appears to be cooperative, but sends a warning message to Koichi to run and hide, while he also procees to scram. Naomasa, Sansa and half a squad are about to chase after Soga, but Midnight reminds the detective they have to guard the hospital, so Naomasa gives a signal to several heroes to catch The Crawler.

U.S.J. Arc
Sansa is among the Police Force members who take the defeated League of Villains members into custody. Before Naomasa leaves to see All Might in the infirmary, he orders Sansa to handle the rest.

Forest Training Camp Arc
The Police Force, Sansa being one of them, come to Kiyashi Ward Shopping Mall after Ochaco Uraraka called. Then, the Police Force temporary closes down the mall to search for Tomura Shigaraki with local Pro Heroes' help, but they are unable to find the suspect.