All Might looked up in shock to see his protégé, Midoriya Izuku standing in front of him.
All Might was kneeling in pain amidst the destroyed Musutafu Kamino Ward. All Might's archnemesis, All For One, had suddenly come back and engaged All Might in a deadly battle. A battle which All Might was losing.
"Young Midoriya!? What are you doing!?" All Might shouted, confused as to the hero in training's actions.
"Saving your life! He's going to kill you if you keep fighting!" Izuku shouted back, turning around to face his mentor.
The suit wearing All For One shrugged and let the conversation play out. Despite his life support helmet keeping his expression hidden, it was easy to tell he was smirking. His entire purpose in fighting was to let his student get away and continue the fight against One For All's user, whether that be All Might or this new kid, he didn't need to win… only keep them busy.
"He'll kill the both of us if you fight him! You're not strong enough yet!" All Might screamed back, scared for the young boy's life. The young boy he was starting to see as a son to him.
"NOT STRONG ENOUGH!?" Izuku shouted at the top of his lungs. "I'D SAY I'M PLENTY STRONG ENOUGH! I'VE MASTERED MY QUIRK, THE BOTH OF THEM!"
All For One's muscles moved as if he had widened his eyes, despite his clear lack of the vision giving organs beneath the mask. Did the boy say he had two Quirks!? Just like before… two Quirks had fused into one. Just as he had the ability to take and give Quirks, his brother could give his own Quirk to others, a Quirk which fused with the strength stockpiling one he gave him. So now that One For All was given to someone who already had a Quirk, both Quirks had fused once again.
That must be his brother's true Quirk! While All For One's kept each Quirk separate, his brother's Quirk fused with any other it came into contact with! It could theoretically end up stronger than his own given enough time and enough Quirks! Simply amazing!
Izuku rounded back to All For One. "So… you're the Symbol of Evil I've heard so much about." Izuku stated, glaring at the villain with determination. "The one who created One For All and who ruled Japan through its underground for decades."
All For One shrugged and chuckled. "I would guess that'd be me. I could see no one else doing it." He answered back pridefully.
"Then… I'm going to beat you, and end this feud between One For All and All For One." Izuku said as he raised his arms ready to fight.
"NO! Midoriya, please, listen to me! He's too strong! He has hundreds, possibly thousands of Quirks stockpiled inside, and he can stack them to make them stronger!" The Number One Hero informed his protégé.
"You might want to move out of the way All Might. I wouldn't want to get you in the crossfire." Izuku warned.
"Here… let me." All For One said before raising his hand and firing off a very small beam of pressurized air, much weaker than the previous ones he was throwing out like candy, and knocked the Symbol of Peace away. All Might was too weak from the fight to put up much resistance.
"Never thought the Symbol of Evil would do that. Despite how much it disgusts me… thank you." Izuku Midoriya, the hero in training known as Deku, said to the villain.
All For One chuckled. "I can always find him again and kill him once I rip your arms and legs off."
Izuku frowned. "I take it back, you're still terrible."
In an instant, All For One had aimed his palm at Izuku and fired off a much stronger blast of wind pressure, one that could tear down buildings.
Once the dust settled, Izuku was revealed to haven't moved an inch. Though he looked different. His skin was black like coal and his hair had disappeared. He had bright red lines markings moving across his body like wires on a circuit board. He had no lips, and instead had razor sharp teeth and two small tusk like fangs coming up from his bottom jaw. His eyes were almost entirely blood red, all except for his irises which were shining purple. His muscles grew far more defined and his toes and fingers were tipped with dangerously sharp talons.
Izuku opened his mouth and smiled, steam coming out as the temperature on the inside of his body raised to beyond boiling. "This is my Quirk. I call it… 'The Ultimate Shield'. It allows me to condense the carbon in me until my entire body becomes as hard as diamonds. Though unlike normal diamonds, I am not brittle. Because of this process, my internal temperatures raise to a point where it will melt even tungsten when put inside me." Izuku said while smirking.
"AND…" Izuku began, before the inner parts of the red markings turned a bright green, as well as more green vein like markings appearing over his right arm. "I can add One For All onto the top of it." He smirked. "In this state… I'm stronger than All Might ever was."
All For One began to chuckle, getting louder and more boisterous until he was eventually cackling like a madman, which he might well be. "Yes. Yes! YES! THIS IS WHAT I WANT! TO BEAT YOU WILL PROVE THAT I'VE CONQUERED THE PAST AND MY MISTAKES! COME AT ME, IZUKU MIDORIYA! COME AT ME SO THAT I MAY KILL YOU!"
All For One burst forward towards Izuku with a speed he had not shown previously, and called upon strength greater than his fight with All Might, and tried to punch Izuku.
But Izuku easily dodged out of the way, before he brought his left fist up and punched All For One in the head as hard as he could. There was a loud crunch and cracking sound as the villain flew into the ground.
As the villain slowly recovered, Izuku looked down at his left arm, and flexed it. "Ouch… got a little bit of a bruise there. Might want to hold back, or it'll sting in the morning." He said to himself.
In truth, he had just fractured his left ulna, and almost broke his radial. Despite his natural toughness, putting One For All on top of his Ultimate Shield still hurt, though he could go full out for a time with it. But he was just putting up a front to anger his opponent. One of the greatest weapons one has is intimidation, and the secret to intimidation is confidence. Appearing near disinterested in the opponent can make them believe themselves to be inferior, even when they are superior. No matter who one is, this works.
It's like not flinching when a gorilla is charging at you, if you stare at it and don't flinch, the ape will turn away at the last second, cowed by your confidence.
All For One leapt back into the fray, and threw a multitude of powerful punches, each of them carrying great gusts of wind, flaming pillars, blizzards or even thunderbolts.
Izuku dodged most of them, using One For All alongside his Ultimate Shield to be as quick on his feet as he could, almost shattering his vertebra as he bent and swivelled to avoid attacks.
But then All For One lashed out with his last punch, this one shooting out a blade of super pressurized water, which turned to steam as cut through the fingers on Izuku's right hand.
The two combatants stood at the ready, as Izuku's magma like blood dripped out of his fingerless hand. The current user of One For All looked down at his hand and chuckled. "I seem to have neglected to mention one last thing…"
One For All was shocked to see red lightning dance upon Izuku's fingers as they suddenly regenerated. "My Quirk is 'The Ultimate Shield', which also gives me the ability to regenerate any injuries I have sustained."
Izuku began to heal his bones as well, as his loss of fingers gave him the perfect opportunity to do so without revealing that he was hurt beforehand. "Even if I lose my head, I can simply make a new body." Izuku boasted. "You can't defeat me-"
Another beam of water cut Izuku off, as well as the left side of his skull. The magma blood poured out as well as half of his brain. The head turned back to normal as it fell to the floor. All For One looked to his fingers to see they were also normal human fingers now.
But then All For One noticed that Izuku's body hadn't fallen over, and was still in the Ultimate Shield state.
"I thought you were smart." Izuku began, speaking with half a mouth made it hard to hear his words, but All For One understood.
Red lightning burst to life around his head as it regenerated, first human, and then more lightning and it turned coal black and soon Izuku was back completely. "Humans can survive with even half of our brain intact. Even less than that. And my Quirk will continue to function so long as even a single piece of my brain still lives."
Izuku spread his arms out wide and smirked at the villain. "There's nothing you can do that can kill me. You can tear me apart, you can't even hurt me… every time you've cut me so far… it's been because I've let you." Izuku put his right hand forward and showed the villain.
He exact spot that his fingers were cut suddenly turned human again, showing that he can control exactly which parts of him were Ultimate Shield and which were not. "I've been toying with you this whole time. Now… stand still so I can end you."
Izuku got into a stance, body positioned low with his hands out front and fingers curled like claws. The very same stance that Mandalay taught him to best use his claws and defensive powers.
"It seems you're truly powerful. Your powers are the perfect combination with One For All. I was right." All For One chuckled. "I'll take pride in the fact that I forged you."
And the two launched towards each other.
All For One called upon every single Quirk he had, and pooled it all into his right fist.
Izuku covered his entire body with One For All, and shot his right hand forward, fingers straightened and pulled together like a knife.
Izuku ducked under All For One's punch, and his hand went through the old man's body like butter, tearing apart his respiratory system and carving a trench through his upper stomach.
All For One looked down at the young boy who had defeated him, and grabbed hold of his arm. "You've done well." All For One used his other hand to grab his own body and pull it apart ever so slightly to give Izuku a better angle.
"What are you…?" Izuku's question was answered when All For One brought Izuku's hand to his heart.
"My job is done… I've forged in Shigaraki's heart the hatred for the Symbol of Peace necessary, and I've forged the greatest hero to have ever lived. One directly, another indirectly. I'm no longer needed here. All the pieces are on the board, and there's no more need for an old fool like me." All For One said quietly.
The camera crew high in the sky caught everything on camera, while they couldn't hear what was said, they could tell that something was being said.
"Very well. I'll defeat Shigaraki, too. I'm not about to let society be brought down because of a few bad apples like Endeavor." Izuku said with conviction.
"Hmm… I guess I'll have a little faith on my deathbed." The Symbol of Evil said.
Izuku jerked back and tore the man's heart out of his body.
Izuku looked up to the camera crew, before he looked back to All For One. "Deathbed? Don't kid me. You'll survive this, and be back for round 2 in a few years. And when you are… I'll defeat you again, and again, and again. As many times as need be." Izuku stated before he dropped the heart on the ground.
All For One chuckled. "Maybe… maybe…" Before he quietened down and stopped breathing.
Gran Torino arrived on the scene alongside All Might and a few other heroes such as Endeavor and Edge Shot.
"Young Midoriya… is he?" All Might asked.
"Dead? No… I don't think so. And even if he is, I don't regret my choice." Izuku told his mentor.
Endeavor stood tall over Izuku. "And who are you to judge whether a person lives or dies?"
"Easy. I didn't kill him." Izuku began, and chuckled when he saw their confused faces. "After I dealt the final blow, he placed my hand on his heart and asked that I kill him. Who am I to deny such a request?"
"You're reputation will be ruined. You'll never become the Number One Hero." Endeavor said angrily.
"And? Look at me. I look like a demon. Even if I was the nicest man alive, I would never become the Number One Hero. Plus, I can think of a few people who have put in much more work than me, and deserve the spot more." Izuku pointed to his scary tusk demon face to prove his point. "Like Momo-chan or Hitoshi-san."
Izuku was covered in the red lightning as he returned to normal, his hair bouncing back into place. "As long as I can save people, that's all I care about." The young hero in training said to Endeavor's face.