Rumi Usagiyama vs. Masquerade Attendees

Rumi Usagiyama vs. Masquerade Attendees is a battle fought between the by then schoolgirl Rumi Usagiyama, under the improvised cover name of Tiger Bunny, and several of the Underground Masquerade attendees.

Prologue
The young Rumi Usagiyama was in the city of Osaka during a school trip when she detected with her developed senses a whiff of a battle taking place nearby. Before her friends can stop her, she leaves there jumping in the direction of where said battle takes place. It doesn't take long for her to reach the location where an illegal fighting event is being held: the Underground Masquerade.

Without thinking twice, Rumi sneaks into the event, and after snatching a tiger wrestler mask from one of the attendees and putting it on, she clings to the ring cage and announces her presence as The Masked Mystery Beauty: Tiger Bunny. Everyone got confused, and some people of the crowd the teases her for having such lame name. Then, one of them recognize her as Usako the Fight Crasher, a schoolgirl from Hiroshima that broke into all fight clubs and vanished after being taken into custody.

Surprised at being uncover so easily, Rumi tries to play dumb but nobody falls for her trick, and some even begin to criticize her for thinking that no one would notice. Having enough of their words, Rumi pipes herself up ready to battle and encourages everybody there to rumble.

Battle
The two combatants who at that moment were actually fighting in the ring, Umeda Siberian and Metro Namba Crusher, stop their battle and politely talk to her about fight etiquette. They scold Rumi for disturbing their fight trying to take all the shine. And about her earlier statement of "let's rumble", both fighters tell her that she does not clarify who she is challenging, and asks her if she wants to fight against Siberian, Crusher or both at once.

Just when they say the last question, both fighters charge at her, but thanks to her Rabbit Quirk, Rumi easily defeats them on the spot with one swift kick. After knocking Umeda Siberian and Metro Namba Crusher out, Rumi smiles and says that these two guy aren’t enough and everyone should join in the fight together next. The ring announcer cannot help but be surprised to see that Rumi has not only defeated his opponents in a flash, but also challenges everyone to fight her, something that's got to be against therules.

Despite this, almost the entire masquerade gets excited by her idea and hops into the ring for a chance to face her, as Rumi defeats them as they enter the ring. The ring announcer cancels the bets as the Underground Masquerade turns into an unorthodox and chaotic one-versus-all match. However, He continues his intense commentary over Rumi 's beatdown of the entire arena.

Fighters, audience members and even some of the Underground Masquerade staff rush into the cage to fight Rumi with their Quirks at full power, and even some carrying weapons, but despite being well out numbered, Rumi is taking all of them down with extreme ease thanks to her rapid and powerful kicks. Not even the power-houses can deal with her attacks. The ring announcer praise Rumi for both her beauty and her prowess in combat.

Aftermath
All For One has been observing the Underground Masquerade through security cameras. He had thought of leaving but after seeing the fights, decides to harvest some Quirks with the help of Kurogiri.

Rumi’s one-sided brawl is immediately interrupted when the alarm goes off, followed by gas starting to pour into the arena. All those who breathe the gas receive a Quirk boost as they lose control and go wild. Then, taking advantage of the confusion, Kurogiri uses his Warp Gate Quirk to generate a small portal through which All For One's hand emerges from it to steals the victims' quirks.

Thanks to the fact that she is above the ring cage, Rumi avoids breathing the gas, but without her noticing the dark mist forms behind her to snatch her Rabbit Quirk. Fortunately for her, the pro Hero O'Clock is also there. O'Clock had infiltrated the Underground Masquerade as a ring fighter to investigate the trafficking of uppers and Quirk-boosting drugs. He also sees what is happening, 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.