This is an idea I've been bouncing around in my head for awhile. Plain and simply Deku's quirk is to learn the quirks of others just by looking at them. Also I decided took give Deku an sister she is not the main focus she will be involved pretty heavily early on but as the story goes on she'll be Less significant she mostly there to add a little variety to the story and keep it from being note for note canon Also this is my first fanfiction but don't hold back the criticism if you think I can improve in any way tell me now onto the story

Quirk Analysis

Chapter 1: Prologue

"Hmm based these x-rays, it would seem that your son does indeed have a quirk ma'am."

A doctor, with a bald head, gold rim glasses, and a moustache so thick it covered, his mouth told a mother and her four year old son. He pointed to an x-ray of the child's foot showing that he had only one joint in his pinky toe which was apparently a way to determine whether or not if someone had a quirk.

"That's a huge relief doctor. You have no idea how stressed I was when Izuku was the only one in his class that hadn't shown any signs of having a quirk, but I would like to know exactly what quirk he has. Is there any way tell, Doctor?" Inko Midoriya said breathing a sigh of relief while her son, Izuku, stood hugging her leg and hiding behind her, but with a smile on his face.

"There are simple tests I perform right now to help narrow it down and determine it. It would help to know what you and the boy's father's quirks are so I at least have a ballpark of what I'm looking for." the doctor said before catching his mistake and adding "Oh and if he has any siblings I like to know their quirks as well."

"Yes of course my quirk is nothing special; I can float small objects to myself. My husband on the other hand is a pro hero, named Mentalist, his quirk automatically warns him about incoming immediate danger allowing him to react and either avoid or counter attack, and Izuku's older sister has a sixth sense. She can feel the presence of people around her even if she can't see them, but her range is pretty limited. That seems to be a stronger version of my husband's quirk." Inko replied to the doctor while Izuku nervously fidgeted next to his mother, looking like he wanted to add a few more details, but he was too shy to say anything.

"Thank you. Ordinarily quirks are inherited from a child's parents, either one of them or some combination of the two. It's also very common for a child's quirk to be stronger than a parents like with your daughter. Knowing that I can try gauge what it is with some simple tests, or I can take a blood test and know immediately. It's up to you want to do Mrs. Midoriya." the doctor stated giving the mother time to think of what option she would want to go with.

After debating for a few seconds, Inko decided the blood test would be the better option. The results would be more accurate and quicker to do so. However Izuku wasn't looking forward getting a shot. The doctor then pulled out a syringe and prepped it to draw blood from the young boy.

As soon as Izuku saw the needle, his eyes went wide and started running towards the door. Inko managed to catch him before he could make it five feet because he was still light enough to use her quirk on him. "Now now Izuku, I know you don't like getting shots, but this is find out what your quirk is. Please wait and let the doctor draw some blood."

"Okay Izuku roll your sleeve up and give me your right arm." The freckled young boy did as the doctor told with tears in his eye not liking what was going to happen next. The doctor then stuck the needle into Izuku's arm and drew blood from him. " See that wasn't so bad was it?"

Izuku nodded while half crying. "Alright now It'll take about a week to get the results Mrs. Midoriya, we'll send them through the mail. Hope you two have a nice day." The doctor said as he waved the family off and waited for his next patient to be called in.

Inko held Izuku's hand as they entered the office lobby. Once there they ran into Inko's husband, Hisashi, and her six year old daughter Izumi. Hisashi is a man standing just shy of six foot tall, with messy black hair, and a toned build fitting of a pro hero. Izumi stood almost a whole head taller than her little brother, with hair the same shade of green as her mother, styled in two pigtails, and missing tooth.

Izumi ran and hugged her brother violently shaking him she asked "So what's your quirk Izuku? Did you find out? Come on tell us." She was still shaking him as she asked the questions, so Izuku could not respond to her.

The parents watched the interaction between the siblings with smiles on their faces. Hisashi laughed a bit before telling his daughter "If you want Izuku to answer your questions you might want to let him go." Izumi didn't know what her father was talking about until she looked and saw her brother dazed from all the shaking. She let him go and apologized. Izuku's only response was incoherent babbling.

"Well Izumi if you really want to know, we didn't find out what his quirk was today. All we found out was he had a quirk. Neither of us know what it is, so we decided to do a blood test. It'll take about a week until know for sure what his quirk is." Inko explained to her daughter and husband.

"I hope my quirk will be something cool like Kacchan's explosion. No matter the quirk I get I'll be a hero just like All Might." Izuku proudly claimed as he imitated All Might's iconic laughter. Hisahi however was a little upset that even though he was a pro hero he wasn't his son's hero.

One Week Later

Inko was in the kitchen cooking lunch for her kids while her husband was on the job who were playing in the living room. Inko watched happily as her daughter chased her son around the room trying make him wear a dress. She called out to them and told them lunch was ready. This caused both kids to stop what they were doing and sit at the table to eat lunch. Seeing as her kids were occupied for a bit, Inko stepped into the hallway to get the mail.

"Kids once you're done eating, come to the living room. Izuku's blood test results arrived and we'll go over them together."

Both kids nodded, finished eating and sat on the couch. Inko opened the envelope and read the letter out loud. "Okay Izuku your quirk is … Quirk Analysis." Izuku looked at his mother confused as to what his quirk did. " You're quirk lets you learn what another person's quirk is just by looking at them, not only that you also learn how the quirk is activated and any weaknesses they have."

"A quirk like that would make it pretty hard to be a hero, but I won't give up. I'll train with dad on how to use my quirk and how to fight." Izuku declared.

Izumi and Inko looked at Izuku admiring his determination. Izumi decided to follow her brothers determination and become a hero as well. She probably would become one regardless but seeing Izuku's refusal to give up it gave her the push she needed to truly go for it.

Three Weeks Later a Park in Tatooine

"Kacchan you're being mean? You're making her cry. You should never be mean to a girl." Izuku said while trying to protect a girl his age with brown hair, brown eyes, and pink cheeks. "If you aren't gonna stop, then I'll stop you myself."

"Do you really think can beat me with your worthless quirk Deku? You and I both know that I'm gonna be number one hero, and you'll never be a hero with such a weak quirk. Even the lowest ranked hero schools won't take someone who's basically quirkless." a boy the same age as Izuku with ash blond hair and red eyes named Katsuki Bakugo taunted while small explosions went off in his hands.

"It doesn't matter if your quirk is stronger than mine because right now you're acting like a villain not a hero. What kind of hero uses his quirk to hurt others? There's no way a bully like you could ever become a hero." Izuku shouted while the girl behind him stopped crying.

She stood up hiding behind Izuku hoping he would continue to protect her. At the same moment something inside Katsuki snapped, and he charged forward screaming. Before he could make contact, the girl screamed "STOP" as she touched him with all five fingers. Katsuki then started to float away before hearing release then he fell face first on the ground.

"Whatever Deku I'm going home." Katsuki said giving up his fight. On his way home he wondered Was Deku right? Was I acting like a villain? Can I really be a hero?

After he left Izuku turned to the girl he helped and asked "Are you okay? Are you hurt?"

"I'm fine nothing hurts. Thanks for the help Deku." She replied.

"Deku?" he asked slightly saddened by the use of that name.

"Yeah that's your name isn't it? That's what he was calling you."

"My name is actually Izuku. Deku is what Kacchan calls me to make fun of me."

"Oh, I'm sorry I didn't know, but I like Deku. It sounds cute. I'm Ochaco by the way."

Izuku blushed when he heard her say that. "You can call me Deku if you want to. Wait your quirk is zero gravity? That's so cool it's a perfect quirk for a rescue hero like Thirteen. I was wondering why Kacchan started floating after you touched him." Ochaco looked stunned.

"How do you know that? I never told you what my quirk was."

"Oh! That's because my quirk lets me learn the quirks of others by looking at them. I have two notebooks with notes on pro heroes and a few of my friends. Wanna see them?" She nodded.

Izuku pulled out two notebooks labelled Hero Analysis for the Future with a picture of All Might drawn on each. He happily showed her his notebooks. They started talking about each other. Izuku learned she had just moved in town and would be going to the same school. As they were talking Izumi came over to the two.

"Hey Izuku. Mom told me to get you. Who's this? What happened while I was in the bathroom? I thought Kacchan was with you. Where'd he go?" Izumi asked her little brother. Ochaco looked at the older girl also wondering who she was. Both looked to Izuku hoping he would explain.

"Huh? Oh right! Ochaco this is my older sister, Izumi. Her quirk is pretty cool she can sense where people are without having to see them. And Izumi this my new friend Ochaco. I saw Kacchan picking on her, so I tried to stop him. That's why Kacchan left. She has one of the coolest quirks I've ever seen. She makes anything she touches weightless." Izuku explained to the two.

"Nice to meet you Ochaco, but Izuku and I have to go home. I hope I get see you again, Ochaco. Come on Izuku let's go. Mom's waiting for us, and Dad's going to be home today after a week." Izuku said goodbye to Ochaco. The two met up with their mother and went home.

And so begins the story of a young boy who would one day become the greatest hero in the world.