Edited 12/7/19 - I will be correcting a few spelling/grammar things in preparation for posting to A03 and writing more for my sister for x-mas. For the people who asked, I'm 100% okay with you using anything from this story in yours, just send me your fic so I can enjoy it too ^.^

Please note: I have no beta reader, there will be many mistakes, if you want them fixed messed me with an edited copy :p I also have a bad habit of not finishing stuff so this will prolly only get a few chapters (hopefully), if anyone wants to adopt the story after I abandon ship go right ahead!

It was about a month after Midoriya Izuku turned four that he discovered the first thing about his quirk. It was a rainy gross, wet and cold day, but it was great because his bestest friend in the whole world Kacchan was over. They were stuck inside, but they were having a blast, right up until Kacchan had started calling Izuku 'Deku' again for not having his quirk yet. It was starting to become something almost mean to say and in an effort to avoid the teasing Izuku suggested they go after the cookie jar that his mother had placed on the top shelf in the kitchen.

Kacchan agreed because Inko made the yummiest cookies, and then they proceeded to drag a chair to the countertop and try and reach up. But four-year-olds are short, so Kacchan yelled for Deku to get on his shoulders while he stood on the chair. Izuku did, and amazingly it was actually the perfect height to reach out for the cookies. The kids' plan would have worked too if Inko had not chosen that moment to open the door to check out why the normally loud four-year-olds were being oh so quiet.

Surprised, the two boys lost their balance and fell to the hard kitchen tile with two shouts and a sickening crack. Izuku, being the one up higher, had smashed his face into the countertop on the way down and was bleeding heavily. He sat crying on the kitchen floor with a bruised, but healthy, Kacchan yelling at him 'not to be a cry baby about it'. In another universe, this would have been the last play date the two had. Inko had not liked how things turned out with her baby's broken nose and his 'friend' yelling at him, and by the time she thought of asking her son if he wanted his friends over again, Izuku had stopped asking for Kacchan to come over.

However, in this universe, Izuku had a quirk. A healing one. About ten seconds into his tears he realized his nose didn't hurt anymore, and a second after that he heard two gasps of astonishment. Izuku's face was fixing itself, the skin almost alive knitting itself around the wound perfectly healing the broken nose. Izuku quickly demanded to watch in a mirror as his quirk came to life. Roughly a minute and a half later the broken nose was cleared and all that was left was flawless skin and some dried blood that his mother cleaned off his face.

And even though it had hurt when Izuku broke his nose (and his mother removed all the cookies from the house) he couldn't stop smiling because he had a quirk and he was going to be a hero!

The second thing Izuku found out about his quirk was three days after the cookie incident when Izuku was at the doctor's. The doctor was a bit confused as to why the son of a fire-breather and a minor telekinetic produced a self-healing quirk, so in an effort to understand the boys quirk more he asked to run a few DNA tests.

Now a lot about quirks is still unknown, but many quirks repeat themselves in a population base and when their DNA is compared Quirkologists can tell you if you have an already existing quirk. There are millions of DNA sets on file so most of the time there was at least something similar to match a quirk with. However, Izuku's DNA did not match anything on file. The closest thing was a complete regeneration quirk that belonged to a late hero that lived during the rise of quirks, but other than a slim resemblance the doctor could not tell the mother and son anything helpful about Izukus quirk, like its limits or its drawbacks.

While Inko worried over this, Izuku was thrilled, he had learned that his quirk was unique and that he could definitely become a hero with it if it was like a hero from the rise of quirks...right? Right. The quirk went down under the name 'Regeneration'.

The third thing Izuku leaned about his quirk was almost an entire year later. Kacchan and him were playing hero and villans with some other kids that followed Kacchan around a lot and had been sitting in a tree waiting to ambush the villains. Kacchan and him were the heroes. Deku was a sidekick according to Kacchan, Izuku was okay with this he just wanted to help people.

Then the boys climbed higher in the tree to avoid being seen by a teacher, probably higher than they should have been. Then it happened. Both boys put all of their weight on to the same one branch. It snapped. The boys fell.

Like it was an anniversary of their first big fall at the cookie incident the boys tumbled down with two shouts, but this time they landed with two sickening cracks. Izuku hit his head hard enough to crack something. Crack something painful in his head. But thanks to his quirk the world just dimmed slightly around him as his skin and bone knitted itself back together. It was hard to judge time when one is half-conscious as their brain repairs itself, but Izuku was sitting up by the time the teachers had made it over to them. Then he turned to his friend.

Kacchan was hurt. He had landed on one leg and had bone sticking out. It was bloody and messy and Izuku felt sick. Kacchan was screaming his head off, and he was...he was...oh.

Kacchan was crying.

He was not crying a lot but Deku could see the small tears forming in his eyes and it dug into his young soul to see his friend like that. He wanted more than anything to help, and his skin started to itch. Suddenly he knew what he had to do.

Pushing the teachers out of the way Izuku placed both his hands on Kacchans compound fracture and activated his quirk. For a second nothing happened, but then Dekus skin knitted itself over the break and Izuku could feel INSIDE his friend. It was strange. He could feel the blood and the bones and he could also feel what needed to be fixed. What Kacchan's body was telling Izuku's quick needed to be fixed.

Izuku willed his quirk to fix his friend, but it was taking a long time (or maybe Deku was still out of it?) When had Kacchan stopped screaming? Deku didn't know. But with his hands still attached to his friend's leg he looked up and saw a face that would be burned into his memory forever. Kacchan was, well everything. He looked shocked, angry (of course), relieved that the pain had gone away... but it was the pure look of awe that struck Izuku. His strong friend that never looked up to anyone was looking at him like that. Like Izuku did the impossbile. The moment lasted until Deku pulled his hands away, letting the skin unknit and leaving a healed leg behind. It was then Kacchan started swearing at him for breaking the branch they had been on and both boys ended up being sent home for reckless behavior.

But Izuku didn't care because not only had Kacchan looked at him with awe for a few seconds straight, but Izuku had learned he could heal other people and help them, and that all he ever wanted.

The fourth and fifth things Izuku learned about his quirk happened later that same night. After his Mother had come to pick him up Izuku had fallen asleep, but his mother could not wake him when they finally got home. Inko panicked and called for an ambulance. Izuku had gone into a minor coma, the doctors telling Inko that regeneration quirks, especially one like Izukus, need a lot of extra food and nutrients to keep up and his normal three meals a day (plus snacks) was not enough. Inko felt a bit like a failure for not testing her son's vitamin levels and much sooner, but the doctor assured her no harm was permanently done and with a new diet Izuku would be fine again soon.

Izuku did learn he needed a higher food intake upon waking up, but he also learned something far more interesting. You see, Izuku may have panicked just a little bit at waking up in a hospital room, his mother had stepped out so he was alone and in his shock, small sparks erupted from his palms.

That was when Izuku learned that when he joins himself to someone else to heal them, his body retains just a little bit of the foreign quirk.

It took a long while for Izuku to learn more about his quirk. He showed Kacchan the small sparks he could make, but Kacchan remained unimpressed. Even at five, his explosion quirk was already strong enough to knock down walls, so small sparks were nothing.

Luckily for Izuku, Kacchan was reckless, and now even more so that he knew Deku could just heal him. This is how Deku figured out the little bits of foreign quirk he gathers stack.

By the time they were six, Izuku could use more than half of Kachans power level. He got more for bigger healing jobs like the time Kacchan fell in a river and got a concussion, or the time Kacchan cut off his pinky toe when he was playing with a knife or the time they made parachutes out of sheets and jumped off the roof or...well there was a lot of times really... He got less from small things like paper cuts that Kacchan always demanded Deku heal. And well, Deku healed everything for Kacchan. Izuku was six, but he knew while he was seemingly indestructible, Kacchan was not, well not without Izuku's help anyways. Not that Izuku said that right out anyways. Kacchan used Izuku as an excuse to do whatever, no matter how dangerous, and both sets of parents had been at their limits. There was only so many times an adult can tell a child not to play with knives or not to jump from rooves, or not to hold your breath until you pass out... And then the boys got into a fight.

You see, even though Izuku healed Kacchan multiple times a day, accompanying him, and pulling him out of danger, Izuku never once got a thank you. That was what spawned the fight that would separate them for years.

The fight went bad quickly, with both boys having a warped sense of what was dangerous they had not blinked an eye at blowing everything up. And did they ever blow everything up. They didn't just blow up one classroom, Deku and Kacchan blew up four of them. Holes in the walls, falling ceilings, broken glass- the whole nine yards. Every student and teacher could tell you have scary this event was. Both boys themselves have hazy memories of this event because they both passed out due to quirk exhaustion.

Both boys were expelled.

But the real fall out was with the parents. Izuku's Mom and Kacchan's went to war with each other. They had been friends their whole lives, but now they both blamed each other for their children's recklessness and getting kicked out of school while ruining it. It was an expensive affair as the school sued and made both families pay for repairs.

Inko decided it was to move to a new cheaper location closer to a new school and hopefully away from the reckless behavior. Kacchan's Mother agreed. They also agreed to not let their children near each other again. For their own safety. Izuku would never give up on his dream though. And he would see Kacchan again at UA like they promised each other.

Izuku learned the most about his quirk is those first few years, but he did not learn anything hugely new about his quirk until a year before the UA entrance exams when Mr. Yagi walked into the hospital that Izuku volunteered at.