On the day that Izuku Midoriya was born, it was obvious that he was going to have a Quirk.
The biggest giveaway was the fact that he was born with 4 arms, each with claw-like hands on the end. He also had fangs akin to a vampire, but they were still small and stubby, like the rest of his newborn body.
His mutation made him incredibly popular at pre-school, as most kids didn't have their Quirk yet. The other kids would ask him to do things just to see him use all 4 of his arms, and they always made him try to do 4 things at once to see if he could.
As the other kids started to manifest their Quirks, this attention started getting less and less as his ability became one of many in the class instead of the only one. The over-attention was pulled off of him for almost a week straight after Bakugou got his Quirk, Explosion.
Izuku, like everyone else in his life, assumed that he wouldn't get the extra-special 4th birthday that all of the other kids got when they manifested their Quirks, because he had his all along.
But even if all his Quirk could do was give him an extra set of arms and fangs, Izuku wasn't going to give up on his dream! He was going to become a Hero, and no-one could tell him otherwise!
There were a few kids who tried to tell him that having more arms wouldn't help him be a hero, but he didn't really care what they thought! His mum believed in him, Kachaan believed in him, and he believed in himself!
Plus, he had done a bunch of googling into heroes with Quirks like his. There were a bunch of Hero's with mutation Quirks! There was Gang Orca, who had a super cool Quirk that made him look like an Orca!
And then there was Fourth Kind! He was Izuku's favorite hero, after All Might of course. He had four arms just like Izuku did, and he was a super cool hero! Izuku had even seen him catch a small car on TV before!
That's why he was going to do his best to train himself, and become a super awesome hero that all the kids like him, the ones that had less flashy mutation type Quirks could look up to!
And for a while, he was successful in training himself for this.
He started to learn the basics of boxing after he asked his mum if he could learn to fight, and it turned out that he had a real knack for it! It also helped that 90% of his opponents struggled to fight against someone with 4 arms.
But when he turned 12 years old, he discovered another aspect of his Quirk, one that would change his views and open up the pathway to being a Pro Hero even more.
He discovered Ether.
It was after one of his boxing sessions that he and his mother discovered Ether.
He had been dead tired, as the guest instructor had pushed them harder than Izuku had ever gone before. Inko had opened the door for him to enter their small apartment and Izuku had slowly trudged his way over to the bathroom to take a bath.
But when Inko didn't hear the water turn on for almost 10 minutes, she knocked on the door, calling out for Izuku, but didn't get a response. She grabbed the master key and unlocked the door and rushed in, worried for her boy.
She let out a scream as she saw him asleep, headfirst in the bathtub, which was full of an odd, bluish-green liquid, vapor softly rising from it. She rushed forward and pulled him from the tub, fearing that he had drowned.
She was confused. Izuku had never even turned the water on! She was sure of it! How could the tub be full of, of, of whatever this liquid was?! Was it a villain trying to drown her son?
She was 'this' close to losing it and having a panic attack when izuku stirred. No coughing, no spluttering as he tried to get the liquid out of his lungs, just a smile on his face as he woke up.
"Izuku! Sweety! Are you OK?! Oh my sweet baby boy I'm so glad you're OK!" She wrapped her arms around Izuku even tighter, and he started getting red in the face, tapping her shoulder until she let him go.
He smiled at Inko, calming her down slightly. "Yea, I'm totally fine! Why? Did something happen? I must have dozed off before I got into the ba- wait, what is that?!"
Inko looked over to where he was pointing, right at the odd liquid that filled the bathtub. She pulled him away from it a little bit before shaking her head. "I'm not sure Izuku. But you had your head under it for at least 5 minutes! That's why I was so worried about you! I thought you drowned!"
Izuku just looked confused. He felt fine! In fact, he felt better than fine! The liquid that was still on him was humming with a sort of energy, and he was feeling more awake than he ever had been just being in contact with it!
He stood up slowly and made his way towards the bathtub. He felt a... connection, of some sort with it. Like he was meant to do something with the liquid. He barely even realized when one of his hands reached out towards it, submerging itself into the liquid.
It felt like a bolt of lightning went through his head as he reached into the liquid. He felt something in the back of his mind click into place as he pulled on the feeling he was getting from the liquid.
And that's when it started.
The liquid started to swirl around his hand, a whirlpool of liquid coming together and forming a small orb in his palm.
Inko was stuck watching in awe as Izuku kept pulling on the feeling, wanting to know what the outcome of this was. He felt like it was important. That it was what he had been looking for.
The liquid eventually formed an orb around the size of a basketball, floating directly over Izuku's palm. Even when he took his hand out of the tub, it followed his hand.
Then, suddenly, as Izuku pulled on the feeling one last time, it all stopped. The liquid had solidified and formed a bluish-green orb. The orb floated up his arm and towards his back, hovering just above his left shoulder blade.
Izuku just looked at his mum in shock at this mouth agape as he tried to form words. Eventually, he succeeded, his mind still reeling.
"Mum, I think we should go see a doctor."
Inko had never agreed with her son more.
"Well, Mrs. Midoriya, it seems like your son has an emitter portion of his Quirk that we didn't know about."
This was one of the first things that the doctor had said their whole visit, other than some small talk and generic greetings. He had given Izuku a once over after he was told about the orb, before giving his 'professional opinion.'
Inko just gave him an 'are-you-serious' look. She was very tired, especially after thinking her son had drowned, and was a bit snippy. "Are you absolutely sure, doctor? I think you should do some tests to be absolutely certain."
The doctor at least had the decency to look embarrassed, coughing into his hand as he looked towards the testing chamber. "Uh, yes, of course. Izuku, why don't you head into the test room so we can begin."
Inko hummed as Izuku nodded, hopping up and walking over to the testing room. The orb stayed in position over his shoulder, following along behind him. The doctor took a few notes, before moving towards the viewing station.
"Alright Izuku, we're going to get you to try and do some different things with the orb to see what it's capable of. We're also going to look into the liquid you told me about, and if it comes from you. Do you understand?"
Getting a thumbs up from Izuku, he nodded to himself and continued. "Alright then. To start with, try moving the orb around your body."
Izuku nodded, closing his eyes as he hunched down and tried to concentrate. He stayed like that for a few minutes, but the orb didn't move. At least not away from his shoulder. The doctor noted that it was starting to shake slightly the longer Izuku concentrated.
They did a few more tests like this, seeing if Izuku could change the shape of the orb, if he could detach it from himself, etc, but nothing seemed to work. The only thing that the long testing session seemed to accomplish was to make the orb shake more and more.
By the time they were done with their testing, the orb was shaking back and forth quickly, enough that it was visible to everyone without the need for the testing equipment. Izuku was actually starting to get worried.
It was just before they were about to head home with the small amount of information that they had gained about the orb from the training session when they heard a crack. Izuku immediately stopped moving and stared at the orb.
For some reason, he felt like this was a momentous occasion. Something to be celebrated. Why did he feel this way? It was just the orb cracking! Another crack.
Then, after a few seconds of the cracks splitting the surface of the orb, the same liquid from before started dripping from the bottom as the orb floated to the ground, and sitting there. Izuku watched it intently as the cracking got worse.
And then, just as he reached for the orb, the loudest crack of all happened, and the two halves of the orb split in two, mist spreading from the center, revealing that the two halves seemed hollow.
That was when Izuku heard it. The soft squeaking sound. The mist in between the halves started to fade slightly, and the squeaking got louder.
And sitting there, surrounded by gas and liquid, struggling to stand up, was a small, 4 armed, 4 eyed creature that looked like Izuku if he was more bug-like. It was about the size of one of Izuku's action figures.
Inko fainted as soon as she saw it while the doctor started taking notes frantically. Izuku reached towards it on instinct, and as his hand neared it the creature grabbed it, giving what Izuku could only assume was a smile.
It made an odd clicking sound, but to Izuku it's meaning was crystal clear. He froze up immediately and looked towards the doctor in confusion and panic. Izuku's voice was squeaky as he told the doctor what the creature said.
"It just called me 'Dad!"