Underground Masquerade

The Underground Masquerade (マスカレード) is an illegal underground fighting event organized by All For One.

Description
The Underground Masquerade is an illegal event that organizes guerrilla fighting tournaments that pit fighters against each other and run the books for the betting audience. The event takes place in the middle of Osaka, hidden in a parking structure. Many are the people who attend to enjoy the pit fights, although they can also be watched through streaming.

The fighting is one on one and everything is allowed in the fight: Deadly moves, weapons, and Quirks are allowed, even some of the fighters use uppers and Quirk-boosting drugs. Due to this, it is normal that one or both fighters end up seriously wounded, needing medical attention, although there is also news of missing persons in connection with this event.

The only known rule is a dress code that obliges all those attending this event, whether they are fighters or spectators, must wear a mask that hides their face.

Event
All For One had organized this clandestine fighting tournament in the city of Osaka to carry out his illicit businesses: illegal gambling, quirk-boosting drugs trafficking, and what was most important to him, the search for Quirks which are worth robbing. Due to the brutality of the fighting, given that the use of weapons and uppers is allowed, it's not strange that the fighters need medical attention after the fight, but there are reports about the disappearance of some of the fighters.

However, it was the trafficking and use of drugs and uppers that brought the attention of Iwao Oguro, know as the Pro Hero O’Clock. Eager for obtaining and secure some evidence of this, Iwao adopts the persona of the underground fighter The Ripper, an expert with the knife who does not need to use Quirk to win his matches. After a series of victories as The Ripper. Iwao finally as the chance to obtain the evidence he needs, and for this, he requests assistance from Tanuma and the police force, asking them to surround the place where the underground tournament is taking place, although not to raid it, but to secure him an escape route after he does what he needs to do there.

With everything ready, Iwao participates in the Underground Masquerade as The Ripper, facing Kendo Rappa, known as The Rapper. After a short fight, Iwao lets himself win and pretends to be unconscious to be taken to another room where injured fighters are supposedly healed. Once there, he “regains” consciousness, and a medical staff member offers him the opportunity to be injected with a special Quirk-booster drug. Iwao drops the act, and uses his Overclock Quirk to knock out the medic and all the accompanying guards. Then, he takes some pictures of hidden documents and the Sick Bay as evidence they're moving illegal drugs.

Iwao plans to sneak out but runs into Kendo waiting for him. He considers that his previous victory was not right as he The Ripper didn't have his heart in the fight, so he hands him half of the prize money. He then challenges for a proper fight, but Iwao, still as The Ripper, quickly declines. As they walking, they hear loud noises coming from the arena. When they arrive, they see that the cause of all that fuss is a young Rumi Usaginawa, who had sneaked into the Underground Masquerade and was defeating a large number of people after having challenged everyone to fight against her, a challenge that many accepted.

All For One had been watching the fights from the security room. He had considered leaving there, but after the turn of events caused by Rumi, he decides to decides to harvest some Quirks with the help of Kurogiri. Suddenly the alarm goes off, followed by a gas starting to pour into the arena. Those who breathe the gas receive a Quirk boost as they lose control and go wild. To prevent anyone from fleeing, All For One locks all the doors to the passages and emergency stairwell, and deploys his subordinates protected with gas masks to ensure that no one can flee. Then, with the help of Kurogiri and his Warp Gate, he steals those Quirks that interest him.

Despite the chaos, Iwao sees AFO's hand emerging from a Kurogiri’s mist to snatch Quirks, and when he notices that the mist is going after Rumi, he uses his Overclock Quirk to quickly jump in and snag her out of the place, avoiding the Kurogiri's dark fog, and returned to where Kendo was. Then, he revealed to him and Rumi that he was the Speed Hero: O'Clock and requested their assistance. Iwao steals three gas masks from some staff for himself and his impromptu allies, as well a prop gun. Then he briefs them about how they are going to escape.

Iwao inform them that there is an exit, but he’s concerned by the black fog that can snatch Quirks, so he askes Kendo and Rumi to make their way while also acting as a decoy, although he request them to not use their full powers on people transformed by the gas. He also comes up with a plan B, in case something unforeseen happens, and instructs Rumi to escape the facility and get the police squad outside to contact Detective Tanuma and ask him to call in All Might as backup.

Kendo and Rumi open the way with Iwao behind them, shooting the security cameras after correctly deducing that whoever is controlling the dark mist isn't currently there. In the control room, All For One is surprised to find that he is losing more and more cameras, as it may interfere with his plans to collect Quirks. However, he was prepared for any contingency as he had already sent a Nomu, the Hooded Man, to prevent anyone from escaping. Kendo and Rumi face the Hooded Man but he knocks them down. Iwao then confronts him, discovering that he is an unusual foe.

All For One sees the battle as best he can, annoyed because the prevailing chaos and the numerous destroyed cameras limit his vision, wondering if he should intervene in person to take over the Quirks, but Kurogiri advises against it, because it could attract the attention of All Might. This concern matters little, since considering that the Hooded Man is a foe too complicated to take down on their own, Iwao puts Plan B into motion. While he and Kendo distract Hooded Man, Rumi manages to escape the building and contact Tanuma outside, giving him the message from O'Clock to call All Might.

Acceding to the Pro Hero's request, Tanuma activates the Might Signal, turning all of the local mascots and advertisements into All Mights, which immediately sends an emergency dispatch request to his private office in the Might Tower. After receiving the request, All Might immediately blasts off to solve the threat. Kurogiri informs All For One that since All Might is on his way, they should retreat, but All For One opts for another solution to buy time, and thus have the opportunity to steal the Overclock Quirk from Iwao, after identifying him as the hero O'Clock.

With the help of Kurogiri and his Warping Gate, All For One places his hand on several individuals in the underground arena, utilizing his powers on each of them to boost their Quirk, transforming them into violent instant villains.

Battles

 * Drunk Lee vs. Master Beast
 * The Ripper vs. The Rapper
 * Tiger Bunny vs. Masquerade Attendees
 * O’Clock, The Rapper, and Tiger Bunny vs. the Hooded Man