When Izuku's quirk came in neither he or his mother were prepared for what would occur on that day. It was two weeks after Izuku's 4th birthday and his Mother was starting to get concerned that he hadn't manifested a quirk yet. While she held nothing against quirkless people Inko was aware of how they were treated by the majority of society now days, and she feared that happening to her son.
As a result, she had called to set up an appointment with a quirk doctor in the hopes that he would be able to give some answers for them. In the meantime, the day before the appointment she had set up a playdate both so Izuku could play with Katsuki and so she could chat with her best friend Mitsuki and hopefully get her opinion on the manner. So as a result, they had gone to a local park so the boys could play while they sat and talked.
Off where they were playing Izuku was beginning to get mad at Kacchan, despite how much he looked up to him. He had gotten his quirk explosion several weeks ago and they both agreed that it was perfect for heroics with all its applications. That being said he didn't like how Kacchan seemed to have become more aggressive and acted like he was better then others. He'd even started insulting Izuku by saying he was probably quirkless or had a weak quirk.
Izuku was trying to talk to him and get through to him how he was acting and as a result they had been arguing for awhile while playing with a marble set they brought. "Just because you have a powerful quirk doesn't mean you can do whatever you want or make you better then others Kacchan!"
Katsuki looked at him with a scowl. "Shut up Izuku, my quirk is strong and that's why I'm going to be the number one hero. Its not my fault the weak quirked nobodies keep getting in my way. You're just mad because you don't even have a weak quirk and so you'll never be a hero."
Despite Izuku's normally calm and cheerful demeanor this began to send him over the edge. "Take it back Katsuki! I'm gonna get my quirk soon and I'll grow up to be a hero that can save others with a smile. Because that's what being a hero is about, saving people, not having a strong quirk." He glared at Katsuki. "If you keep acting the way you are now, you'll never be a hero, you're acting more like a villain!"
Katsuki let out a snarl at this and small explosions began to let off in his hands. "Shut up shitty Izuku! Being a hero isn't about saving nobodies its about being strong enough to beat the villains! That's what being a hero is all about. Its why All Might is the number one hero, because he always wins! Just like me!"
Upon this exclamation he gave out a shout and shoved Izuku down while using his quirk. Now in all fairness while Katsuki certainly had a strong quirk, he was all the same still a child. So, the explosion let alone the push still weren't that strong in truth. That being said, they were still loud, bright, and frightening. Especially to the two Mothers sitting nearby who had looked up from their talk just in time to see the two boys come to blows and go up in a cloud of smoke and dust.
The two quickly started running towards the boys with Inko yelling out for Izuku and Mitsuki exclaiming "Oi brat what in gods name do you think you're doing attacking Izuku like that?" As the dust began to clear Mitsuki grabbed Katsuki by the ear angrily asking what the hell he thought he was doing as he growled and told her to get off of him. As this happened Inko reached down trying to grab Izuku through the smoke to check and see if her baby was ok, but upon seeing Izuku she froze.
Izuku was halfway rising up from the ground and was reaching up brushing a bit of blood and soot off hid face. As earlier stated, the explosion wasn't truly powerful enough to hurt Izuku besides a minor burn and a few scrapes. Inko was relieved to see this but the reason she froze upon seeing him was due to the fact that Izuku had green lightning crackling around his body and running up and down his arms.
Izuku got up glaring (as much as a 4-year-old can) at Katsuki the whole while. Green lightning was still crackling around him, and the others were now looking at him wide eyed as well. As he had fallen on the ground Izuku had unintentionally grabbed a few of the marbles that the two boys had been playing with. However instead of remaining in the palm of his hand the marbles seemed to be floating around his hand, seemingly caught up in the emerald electricity like satellites orbiting a planet. Letting out a sudden yell of "I told you to stop being a bully Kacchan!" Izuku swung his arms forward and they were all momentarily blind and deafened from a flash and thunder crack.
As they slowly regained their sight Mitsuki suddenly stuttered out "Inko look over there!" pointing towards a large boulder that was set off the side of the playground as decoration and for kids to play on that had been in the general direction that Izuku had been pointing. Despite most likely weighing several tons the rock lay shattered in several pieces and had several molten holes through it with bits of electricity arching around it.
As they stood there looking on what could only be described as carnage, they heard a groan and a thud behind them causing them to whirl around to see Izuku had apparently collapsed exhausted on the ground. Inko frantically ran over to him and started looking over him trying to see if he was injured in any way. Mitsuki and Katsuki just stood there eyes wide and jaws hanging as they looked at the destruction caused by something as simple as marbles.
Soon enough some local heroes came by to see what was happening and Mitsuki snapped out of it and explained to them that Izuku had awakened his quirk causing the destruction and him to pass out. After being told of the situation the heroes were very understanding and helped provide basic first aid to Izuku when he woke up. Izuku was rapidly switching between awe at his quirk, shame for almost hurting Katsuki and his Auntie Mitsuki, and fanboying over the heroes who had stopped by. Yes despite what happened today some things never change, Izuku is still a hero fanboy above all else.
After this occurrence Inko and Mitsuki decided it would be best to end the day there and worry about the boys fight later. They figured with such a volatile quirk it would be best to get Izuku to a doctor soon as possible to get him analyzed so they could learn how to deal his quirk in a safe manner. And find out exactly what his quirk was as it was like nothing Inko or Hisashi's quirks so they would have no knowledge of how to help him with it. Thankfully in this day in age quirks needing a quick response were a common enough occurrence that Inko was able to get their appointment moved to that afternoon.
The Doctor was a rather odd man, at least in Izuku's rather limited opinion on the matter at least. They had filled out paperwork explaining what had happened and details of his quirk that they had seen before they went into his office so the man already knew some of the details. He was muttering rather incomprehensibly with only the occasional phrase such as "powerful", "amazing", and a few others being understandable. This in and of itself wouldn't be enough to bother Izuku as this was already a habit, he had developed himself whenever he found an interesting quirk. All the same something seemed off about the man so he stayed closer to his mother then he might have otherwise.
Eventually Inko cut in and interrupted the mans muttering. "While I'm glad you find Izuku's quirk so interesting I'd appreciate it if you could actually help us figure out what it is. His father's quirk was fire breath and mine is minor telekinesis, so I don't know how he has some sort of." She trailed off here clearly unsure what exactly it was Izuku had done earlier that day. "Some sort of super strength or lightning quirk? What's going on doctor, please tell me so I can help my son."
The man quickly cleared his throat and looked up at them slightly blushing. "Ah yes of course my apologies Mrs. Midoriya. I just got a little caught up in theorizing what your child's quirk might be. While my fascination with quirks certainly makes my job a joy for me it does sometimes lead to me getting distracted. Before I put forward any ideas of what I think Izuku's quirk is I'd like to try running a few simple tests if that's ok with both of you?"
Inko nodded slowly. "Of course, that makes sense doctor, do what you need to do to figure things out." She paused here for a second. "As long as its safe of course." While she hadn't found the doctor quite as odd as Izuku did she was still a mother, and he was obviously very eager to dissect her son's ability.
The doctor laughed sheepishly. "Of course, of course not to worry Ma'am, its just a few tests and they will all be perfectly safe." Having said this, he went to a drawer where he got something out and then returned to his seat. He sat down and looked at Izuku now slightly more serious than he was before. "Alright young man I have a theory for what your quirk is, but I need a few things to confirm it. Here I have a beanbag that we use for testing different quirks sometimes. I'm going to set this on the table here and I'd like you to reach out your hand towards it and concentrate on trying to push it."
Izuku looked at his mom who nodded before he reached out his hand and concentrated. With a sudden gasp his arm surged with green lightning and a wave of force hit the bean bag shooting it across the room and into the wall where it exploded on contact. Inko and Izuku stood their eyes wide looking at his arm which still crackled with emerald sparks. The doctor through his head back laughing upon seeing this.
"Yes, it seems I was at least partially right about what your quirk is. Now before we say anything for certain we still have a few more tests to run." He pulled out a second bean bag which he put down in the same spot as the first. He turned to Izuku again. "Alright now child, this time I'd like you to try pulling the bean bag towards you instead of pushing." He paused here for a second with a winch and quickly added. "Ah but I would recommend that you try to use less force this time, and probably don't try to catch it with your hand. Assuming you can pull as well as push you might still have the raw strength and while it wouldn't really damage you, I doubt you want a bean bag smashing against your hand."
A bit more hesitant this time Izuku still raised his hand to the bean bag again and with a look of concentration it launched across the room in his direction to which he gave a quick yelp and ducked out of the way just in time.
The doctor smiled and nodded. "Yes, I thought that might be the case. As I'm sure the two of you know most children inherit a mixture of their parent's quirks. Sometimes a child will have a random quirk appear or possibly one will resurface from several generations past. At first from reading the report on the incident this morning I thought that might be the case. But I now in face believe that your son is the third type of quirk development. Some children develop a supercharged or evolved form of their parents' quirk. That is what your son has I believe, a supercharged version of your simple telekinesis. While I doubt, he will develop true telekinesis and be able to move items three dimensionally I think your son will develop over time the ability to apply incredible force on objects with telekinesis that most who have true telekinesis will never develop. I also suspect from the lighting going all over his body that he may with time be able to shoot telekinetic blasts and pulls from any part of his body at will. Such as his feet, back, or even eyes."
He paused for a second while the two Midoriya's stared at him in wonder at what he was saying. He cleared his throat before continuing. "Although to be honest I would recommend you take caution using any sort of energy around your head. And especially your eyes as they're delicate organs and not meant to have too much force on them. But regardless you'll discover the limits of your quirk in your own time. But no matter what ends up happening in the future." He smiled at Izuku. "Congratulations young man, you have the perfect quirk to be a hero."
And with that the green haired members of the room simultaneously burst into tears and hugged each other in happiness while the doctor sweat dropped. And that is where the true story of Izuku D. Midoriya began.
AN: Two things I wanted to address. First the lightning. Yes I know that's a side affect of One for All in canon but I love the visual affect and decided to add it to Izukus birth quirk in this story. It will come more into play later on in the story as well. And second calling him Izuku D Midoriya. Yes thats a one piece reference. No this isn't a crossover. I've just been binging one piece recently and thought it would be fun to put in.