Kaina Tsutsumi/Synopsis

History
Lady Nagant was a Pro Hero that worked for the Hero Public Safety Commission, joining the organization at a young age with a bright sense of optimism at becoming a great Hero. Her precision with her Rifle Quirk was envied by the likes of Snipe and other heroes with long-range Quirks. However, the Commission primarily used her for classified missions, secretly disposing of Villains planning to commit acts of terrorism and corrupt Heroes seeking more fame and fortune. The stress of the seemingly never-ending string of murders continued to get to her, all the while needing to keep the front as a public Pro Hero. One day, she came across a group of kids who wanted to shake her hand, leading her to hallucinate her completely bloody hand, and resulting in her questioning her purpose as merely just a cog to maintain the phony illusion of their society.

When the then Public Safety Commission President ordered her to make two corrupt Heroes who were taking advantage of the system "go missing", she questioned if killing them will solve anything, and if keeping these secrets is just the equivalent to brainwashing. The President insists that all this is necessary to preserve the faith in Heroes, but when she continues to voice her resignations, he threatens her by saying it isn't a job you can simply walk away from. In response, she kills him. She was soon arrested and incarcerated in Tartarus, as the Commission covered up the President's death, claiming Lady Nagant's arrest was due to killing a fellow Hero in an argument.

Paranormal Liberation War Arc
Within hours after the end of the Paranormal Liberation War, Tomura Shigaraki, possessed by All For One, started an assault on Tartarus with his accompanying Nomu. Inside the prison, an EMP attack shuts down Tartarus' monitoring system, and ends up freeing all of its inmates, including Lady Nagant. As the inmates start attacking and killing the guards, Lady Nagant makes her escape, noticing how the system isn't responding to their Quirks, before noticing that an inmate banging on his door, unable to escape. Lady Nagant uses her Quirk to open the door, and out come rushing is Kai Chisaki, desperate to reach out to his boss.

Shortly after the breakout, Lady Nagant is approached by All For One, who is honored to meet the traitor of the heroes. All For One asks Lady Nagant for a favor, considering her to be leagues above the other escapees. He explains that a boy would be certain to leave U.A. High School, so he wants her to capture and bring the boy to him. Lady Nagant interrupts, insisting that she has no interest in anything but escaping Tartarus. All For One convinces her that so long as the boy lives, the collapse of hero society she sought will never arrive, so she reluctantly accepts his proposal.

All For One notices the mentally broken Kai muttering about his boss, and asks if he's a friend of hers. She denies this, but sees use in Kai's broken state, so she brings him with her. To seal their deal, All For One offers a gift, and transfers Air Walk to her.

Villain Hunt Arc
One night on a rooftop, Lady Nagant, accompanied by Kai, fires a bullet and hits Izuku Midoriya's phone using a sniper rifle protruding from her right elbow. With the phone pinned to a nearby wall, Lady Nagant talks to Izuku through a microphone inside the bullet. She tells him that if he complies, she will keep his limbs intact. Izuku then moves, prompting Lady Nagant to fire at him. As he is avoiding her shots using Blackwhip, she curves a bullet and lands a hit on Izuku, although he figures out her location and makes his way towards her.

While retracting her rifle, Lady Nagant notes that this is the first time anyone has deflected two of her bullets. Kai then blankly mutters that he wants to get back to his boss. Annoyed, Lady Nagant picks him up and tells him to hide, and begins having second thoughts about bringing him along. Using Air Walk, she goes to finish her mission.

Lady Nagant swiftly moves through the air and shoots two bullets at Izuku from different angles, with one getting deflected and the other grazing Izuku's stomach. As she shot once more, Izuku unleashes a massive smokescreen, catching her off guard. Now knowing that Izuku has multiple Quirks, she repositions up away from the smoke, aiming at Izuku again. She shoots at moving figures, only to learn that they are decoys. She tells Izuku that he can't hide in the smoke for long, but is surprised when he charges out of a building and grabs her arm.