Kai POV

A wave of villains run towards me ready to end me. I jump up and slam my fists into the ground sending them away. A four armed dude repeatedly tries to punch me and nearly comes close. I redirect to my reaction time and dodge his fists.

Four Arms: "Stand still and let me crush you!"

I catch his fist and kick his chin. He goes airborne as Aizawa kicks him back into the dirt knocking him out. I limbo as a woman with giant arms delivers a right hook. I kick out her legs and grab her arm. 

I then slam her onto the ground as she screams in pain. I look forward to see multiple villains aiming at me. I boost my durability and watch as their attacks strike me. I smile as I'm not taking any damage. They cease fire and become shocked.

Villain: "Why aren't you hurt!?"

I half smile and lift up a section of the ground. I then toss it like a frisbee knocking the villains down. A guy with four legs rushes in and tries to kick me. All four legs come down forcing me to roll to dodge. That's when Four Arms grabs my ankle and laughs. 

I'm swung around and thrown into the air. A guy with cannon fingers aims and fires a barrage of bullets launching me further upwards. Luckily before I can go through the roof Aizawa wraps his scarf around my wrist.

We both pull rocketing me towards the ground. I boost my strength and punch the ground. A massive ripple goes out sending every villain in the area away. I get to my feet and see the villains looking at me in fear.

*with villain* 

Shigaraki: "Kurogiri, who is that kid?"

Kurogiri: "According to the files, he's Kai Midoriya. Says his quirk lets him boost his body."

Shigaraki: "He possesses great power, he might become a problem to our mission."

Kurogiri: "What're you suggesting?"

Shigaraki: "We take him out of the equation. Nomu, you're up."

Nomu roars before running full speed towards Kai.

*with Kai*

I punch another villain out cold when something big makes its way to me. I look and see that massive creature heading for me. I boost my body further as it slams its fist into my ribs. Despite my boost I feel two ribs break, the thing sure packs a punch.

Before I can counter attack the creature grabs my head and partially spins around. It then chucks me into the air clear past the USJ's roof. My momentum carries sending me into the far distance.

*at UA 3rd POV*

Nezu: "Which brings us up to why you should be more careful when heroing. I-"

Kai comes crashing through the roof stopping in between Nezu and All Might.

Nezu: "That's one way to make an entrance."

All Might: "What the hell Kai!?"

Kai: "The students need help. Villains have breached the USJ. Aizawa's holding them off but I fear he won't last. There's also some kinda creature with some real power up it's sleeves."

Nezu: "Assemble the other teachers. This situation just became urgent."

All Might: "Will do."

He presses a button on his phone which makes the sirens blare. Kai meanwhile gets to his feet while holding his ribs.

Nezu: "You're hurt."

Kai: "I'll be fine. We need to hurry."

After a few minutes every teacher in UA begins the march towards the USJ. About halfway there Kai sighs while falling to his knee.

Midnight: "You okay?"

Kai stande. Whenever Deku is in danger a kind of feeling hits Kai, telling him he needs to hurry to his brother. This feeling combined with the danger still at the USJ ignite something inside Kai. His knuckles whiten as his quirk begins boosting his body to the max. 

His eyes become solid white as his hair stands on end. A red aura surrounds him. His transformation shocks every teacher as Kai crouches down. He runs away leaving a sonic boom in his wake.

Nezu: "Oh dear, we must hurry. I fear more than just the student's safety now."

The teachers nod and double their pace. Meanwhile back at the USJ things have just gotten worse. Thirteen is out of commission and Aizawa is laying in a pool of his blood. Nomu has Deku as his mercy and Shigaraki is one touch away from making Tsuyu wither away. Through the bleakness the doors leading inside are blown clean off their hinges.