Okay, before anyone says anything, I know I have many more fics to update. I was going to hold off on writing this, but it would not leave my mind no matter how much I tried. It was giving me writer's block for the other fics thanks to all my thoughts coming back to this fic. Now that I have the first chapter out, I can work on my other fics ^^
Note: Please do not ask me when I will be updating my other fics or to update another fic. I know everyone wants me to update them, and I am doing my best to work on them. So please only leave reviews about this fic.
I do not own One Punch Man or My Hero Academia. They belong to ONE and Horikoshi respectively.

Chapter 1: The Strongest Teen

Quirks. Magnificent superpowers that approximately eighty percent of the human population possesses. These powers originated several generations ago with the sudden emergence of them in across the planet. Over the years, these powers have spread across the planet. However, with the emergence of these powers, came chaos. Thanks to selfish desires that lurk among humans, crime rates soared and the police were overwhelmed. Many people perished, but individuals began to rise. They were known as vigilantes, but they fought against the chaos that police were unable to handle.

People were inspired and more vigilantes rose. The ensuing fights between both sides were violent and brought more chaos to the world. The governments of each country saw how much trouble this was causing. The police force were chasing both sides since both were considered villains while the vigilantes had to work on their own which caused more casualties thanks to knowledge that would have proved useful. So to help solve their problems, they all started a new occupation: Pro-Heroes.

Now people who possessed the will and desire to save others could sign up and become official heroes. These heroes worked alongside the police force and were able to bring criminals to justice much quicker and with much less damage being caused. Vigilantes were still considered criminals though this did not stop some people from continuing this profession.

A few generations later, and we see the rise of the world's greatest hero: All Might! The No. 1 Hero and Symbol of Peace. With the work of this hero and his overwhelming strength, crime rates plummeted, and the world became a generally safer place than it once was.

The profession of hero has also become vastly more popular. All across the world, hero schools have sprouted up to teach every generations' batch of hero prospects. The most popular hero school though, U.A. High, is the school that some of the most popular heroes have graduated from. The most famous example being All Might. The only downside to this though is the fact that many new heroes have chosen the profession solely for the fame that comes with it. Most do not complain because they still do their job of protecting citizens, but some argue that if new heroes are only in for the money and fame than can everyone truly count on them?

With the history of the Quirk side of the population over less focus on the quirkless side. Otherwise known as the other twenty percent. Thanks to most professions being focused around the use of Quirks or being Quirk biased, the Quirkless citizens are regarded ratherly negatively by many people. Some being treated so badly that their lives end prematurely. They can be treated like they are not even human. Sometimes they are treated even worse than animals or insects if they live in a harsher neighborhood. And with every new generation, the Quirkless percentage decreases further and further.

Thanks to this, Quirkless people usually give up on any dream of ever becoming a hero because they believe they could never compete with the Quirk-wielding heroes. So they tend to find professions that will still hire them although they often are paid less than their co-workers with Quirks that help the job move along faster.

In the end, in a Quirk-based society, the Quirkless population have a hard time making a living. However, even with the odds against them, not every Quirkless person has given up on their dreams.

Present Day, Musutafu

"Fear me! I am Vaccine Man! I have been gifted my Quirk to save Mother Earth from the disease that is humanity! Bring me your strongest heroes and I will destroy them!" a tall, muscular purple man shouted as various citizens and Pro-Heroes lie scattered across the road. From the antennae on its head, a ball of energy formed before shooting forward and smashing into a building. The building screeched before slowly collapsing to the ground.

Vaccine Man frowned as he looked around and noticed the lack of Pro-Heroes coming for him. "Are you scared of me! Come so I may crush you under my heel before I finish off the rest of humanity!" he yelled angrily as he smashed his foot down onto the ground resulting in a small crater forming. The sound of a cry caught his attention as he looked over and noticed a small girl crying. Frowning, he walked over to her and brought his hand up.

Spreading his claws, he moved to slice her to pieces to help show how serious he was about his ambition only to pause as the girl vanished from sight. Blinking, he smirked cruelly as he realized that a hero must have shown up. Rising to his feet, he looked around before his gaze landed on a short figure wearing some kind of yellow costume with a white cape.

Narrowing his eyes, he moved to address the hero...only to realize that this 'hero' was in fact a kid himself. Well teenager would be more applicable a term, but a kid nonetheless. Must be some kid with a speed Quirk who decided to play the hero. Poor brat, he was about to discover why children should never do something so stupid.

"What are you doing brat? You are not a hero. If I did not plan to destroy humanity I would have given you the chance to run, but sadly I am," Vaccine Man smiled as he moved towards the costumed teenager. As he moved closer, the teen lied the girl he saved down and rose to his feet while twirling around to face him.

The most notable features that struck out to the villain was the kid's bland face. He looked like he was bored out of his mind with little else going on to interest him. The other feature was the kid's bald head. Quite odd for a child so young to not have any hair, but it might be genetic so he wouldn't judge the kid.

"I have come to stop you. I am Saitama, a hero for fun," Saitama announced while staring Vaccine Man down. Vaccine Man paused as his eye began to twitch. What...the...

"Hell! What kind of crap backstory is that?! I was gifted this Quirk to save the planet from the pollution of humanity! I will save the Earth from the disease that is man- Argghhhh!" his dramatic speech was cut off as a fist collided with his face and sent him flying through the air, through several cars, and into a building. His consciousness faded immediately, and all he saw was black.

The teen stood frozen in place with his fist still out stretched. His eyes narrowed as he slowly brought his fist closer to his face. "Just one punch again...Damn It!" Saitama yelled angrily to the sky. After allowing his anger to flow out, he let out a small growl before turning and heading back towards his house. School started in a hour.

As he disappeared from view, the police and the heroes, Death Arms and Kamui Woods rushed onto the scene. Looking around, the two gaped as they noticed the destruction. Keeping their guards up, they ran around searching for the villain that caused the destruction.

"The last report we got from the Pro-Heroes that were fighting the villain was that it was insanely strong. We might not have a chance ourselves, but if we can hold it off long enough than some of the stronger pros can get here," Death Arms told Kamui as they continued looking around; occasionally, they paused to check on the unconscious citizens and heroes that littered the ground.

As they turned a corner to continue their search, one of the officers called out for them. Rushing to his side, they gaped as they looked down at the figure lying at their feet. The villain that was described to them was lying unconscious at their feet with an imprint of a fist on his left cheek, several teeth lied around him, and he was clearly out cold. Someone must have gotten to him first. The fist though...could All Might be in town?!

Aldera Junior High

Letting out a yawn, Saitama walked into the classroom and sat in his desk. After getting home and washing off the dust and blood, the villain's, Saitama changed into his school uniform and rushed over to the school. Everyone avoided him like usual, not that he really cared. They were all jerks honestly. The only person who talked to him was-

"Saitama-san! I didn't see you on the way in! Usually, we get to school around the same time," the shorter green haired student told him as he rushed in and sat in the desk next to Saitama's. Saitama groaned at the loud voice before turning to look at him. The student's name was Izuku Midoriya. They met around five years ago when he spotted the kid getting beaten up by some blonde haired jerk with an Explosion Quirk. Stepping in, he attempted to help out, but also ended up getting beaten on. Izuku appreciated it though, and the two became friends over the years; especially, when they found out they were entering the same middle school.

"That was back when I still had hair...*sigh...*" Saitama groaned out into his arms which earned him a confused look from Izuku. Looking up at him, Saitama let out a sigh before saying, "Sorry, I had something to do before heading over. I'm surprised I beat you here. Was there a crime somewhere?"

Izuku's face went red in embarrassment as he scratched the back of his head. "Well, there was a fight going on between one of the heroes and some new villain with a tree-growing Quirk! ItwassocoolbecauseitlookedsomuchlikeKamuiWoodsQuirkbuthewasabletogrowthetreesfromthegroundandbuildingsandallsorts-" Saitama felt a vein in his forehead begin to throb. They were friends sure, but this annoying habit of Izuku's...

"Keep it to 20 words or less!" Saitama smashed his hands down on his desk, leaving an imprint of them on the surface, while glaring at the startled hero fanboy. The entire class paused to look at the two before shrugging it off and going back to their normal business.

"S-sorry, um, the villain had a tree-based Quirk. It reminded me of Kamui Woods which I thought was cool," Izuku explained with a red face. Saitama pinched his brows as he leaned back in his seat and nodded his head. Kamui Woods was popular in their town, and Izuku had a fascination with his Quirk so a villain with a similiar one would definitely interest the fanatic.

Relaxing back into the comfort of his arms, Saitama began to drown out the rest of the students filing in along with the teacher. He clocked back in when he heard his name for roll call, but immediately zoned back out. His mind went back to this morning. That villain he fought in town. Clearly he was strong...at least compared to the Pro-Heroes that fought against him, but he defeated it with one punch. This has been happening ever since about one and a half years ago when he first noticed his hair was falling out.

He was suddenly super strong and any villains he encountered while out doing his exercises could not stand a chance against him anymore. It was irritating. There was no more challenge. No more thrill. He originally became a hero because it was a small dream he had before finding out he was Quirkless. After he found out, he gave up on it and decided to try to have a more obtainable goal. However, that all changed when...

"Oh Saitama, you're trying out for U.A. as well?" the teacher's question finally penetrated Saitama's mind causing him to stir and sit up.

"...What?" Saitama asked in confusion which earned a round of laughters from the rest of the class. Looking over to Izuku for some answers, he blinked before saying, "Why are you on the floor?"

Izuku looked back at him in shock while a blonde boy who had just sat back down growled in anger. As he got back up to threaten Saitama like he did with Izuku, the teacher cut him off, "Now now Katsuki, that's enough of that. Class needs to continue."

Saitama looked back at the fuming Katsuki who slowly sat back in his seat before glancing back at Izuku with a confused expression. Izuku just sighed as he pulled his desk back up and sat down while trying to steel his nerves. Deciding to ignore whatever was going on, Saitama zoned back out.

For the next few hours, Saitama went through the motions so school could hurry and pass on by. He was not really a fan of school. His grades were not the best even with Izuku's help. However, they were passable enough which kept his parents from nagging him about them.

The teacher had mentioned that he signed up for U.A. right? Honestly, he only did it because he knew Izuku was, and he did not know the names of any other high schools near his home. So it seemed like the best option. Plus, he was a hero. It made sense to go to a school for heroes.

At the sound of the bell which he had conditioned himself to always be on the lookout for at school, he immediately reached for his bags so he could begin packing. "Deku." Saitama barely heard Katsuki say. Weird nickname for Izuku. According to Izuku, the two boys are childhood friends, but all he noticed since he began hanging out with the green-haired boy was that Katsuki was a bully. Nothing, but a bully. Or prick. Any insult would work for him. Izuku saw it different though. Maybe he was trying to hold onto to what small friendship the two had before whatever happened.

"K-kacchan," Izuku responded with a stutter. Also a weird nickname. Kaa-chan means 'mom' so why does Izuku call Katsuki, mom. The boy was far from motherly. Oh well, not his problem. Izuku asked him to not interfere with any confrontation with Katsuki which he respected. He only stepped in if Katsuki took it too far.

Continuing to pack his bag, he allowed himself to eavesdrop every few seconds. The usual seemed to be coming out of the explosive teen's mouth. 'Useless.' 'Not going to happen.' 'Give up' Nothing serious...at least...

"If you really want to be a hero, why don't you take a swan dive off the roof. Maybe you'll be reborn with a Quirk in your next life!" Katsuki laughed as he moved to leave with his two lackeys. Saitama froze for a second before moving to catch up. Izuku was standing in place behind them.

"Hey Katchi," Saitama called out while intentionally saying his name wrong. Seeing the flinch, he knew Katsuki was about to turn and yell at him. Waiting for it, the second Katsuki turned to look at him Saitama allowed some serious intent to flow through his body. Doing this before, he's noticed how some weaker criminals would freeze in their tracks. It was never useful since all he wanted was a good fight, but now seemed like a good time to do it.

Realizing that the three teens in front of him were momentarily frozen, Saitama brought his hand up to Katsuki's forehead, "Say anything like that again...and I'll punch you," before flicking him. The boy's body lurched backwards painfully from the force behind the flick while the two lackeys yelped and ran down the hall. Katsuki, on the other hand, fell to the floor and cradled his aching forehead. Saitama gave one last glance before walking down the stairs,

He was not the best with words or comfort so he knew it would be best to give Izuku some alone time to try and recover from Katsuki's words. "Maybe I'll hit up some sales in town. It will get Kaa-chan off my case when she sees my report card," Saitama muttered to himself as he headed towards the shopping district.

As he left the campus, Saitama allowed his thoughts to wander. He applied for U.A. sure, but where would he go if he didn't get in? Most students were trying to find schools with hero courses, but he did not need to worry about that since he already was one. He does not make any money doing it though which really sucks. It's gotten so bad, he has began to collect coupons for sales at different grocery stores like his mom did. "Ugh, I feel like I've already became an old man. Great! Like being bald wasn't bad enough!" Saitama internally complained as he let out a sigh and hunched forward.

"Agh! Watch out!" a voice yelled out which was followed by countless screams. Saitama ignored it though and kept walking down the sidewalk. "Move baldy!" the voice shouted with desperation in its voice. Saitama froze in place while his gaze hardened. "I told you to-GACK!" the voice screamed as Saitama's fist impacted with it. Turns out the voice belonged to some kind of Slime Villain as pieces of the person shot out all across the street.

"WOOAAAHHH! That was unexpected!" a loud booming voice shouted as a shadow fell over Saitama. Looking up, Saitama was somewhat surprised to see the Number 1 Hero, All Might, standing in front of him. Blinking at the man's large smile, he shrugged and waved good-bye to the hero as he turned to continue on his way, only for the man's hand to fall on his shoulder, "Now now, young man, where are you going?! I still need to thank you for stopping that villain for me! I've been chasing it for quite awhile today!"

Saitama looked up at him blankly, "Ok." All Might's eyebrows furrowed at the teen's blank face. As he moved to say something, Saitama pointed back at the manhole behind them. "That guy pulled himself back together and slithered down there by the way. I didn't punch him hard enough to knock him out completely," Saitama explained before walking off while All Might groaned and dashed pass Saitama and into the sewers.

Ignoring the looks the rest of the civilians were throwing him, he walked into one of his favorite stores. "I wonder if they have any kombu in stock today," Saitama muttered to himself while absentmindedly rubbing his head...before pausing and ripping his hand back down to his side.

An Hour Later

Saitama walked down the street with his groceries in hand. Holding the cell phone up to his ear with his shoulder, he muttered annoying, "Yes kaa-san, I'm on my way home now. I stopped to buy some groceries. Yes yes, I bought some crab meat, I had a coupon to lower the price. Uh huh, uh huh, *BOOM!* yeah I got it-what? Yeah that sounded like an explosion. Don't worry, I'm not even near it. Yeah yeah, kaa-san, you worry too much. Hey! I can take care of myself if worse comes to worse! Yeah yeah, I'll see you at home."

Reaching up, he took the cell phone from between his ear and shoulder to place in his pocket only to stumble as the ground shook. Sadly, his cell phone fell and hit the corner of the sidewalk breaking the screen. Sighing, Saitama picked it up and looked in the direction of the explosions. "Whoever is doing that owes me a new phone..." Saitama grumbled as he dropped the phone in his pocket and headed home.

At least that was the plan. "Hahaha! With all the heroes focusing on that villain, I can rob and cause as much destruction as I want!" a tall villain shouted. Saitama blinked at the villain's costume design. He wore a skin tight suit that showed all his muscles, an odd helmet with two eye holes cut out, and fingerless gloves. He was really tall, probably nine feet tall in fact.

"Hey. Knock it off. There's clearly something else going on. If you're going to rampage wait until the other heroes aren't so busy," Saitama shouted out to the man who looked over and glared down at him. Almost immediately, the man brought his fist down on top of Saitama sending dust flying everywhere while causing the ground to shake.

"Stupid brat," the man muttered as he moved to leave only to yell in pain as he felt something sharply grasping his wrist. Looking back down, he was surprised to see that the teen that he thought he killed was standing completely unharmed while gripping his wrist with one hand.

"I told you to leave and come back later, but oh well," Saitama muttered as he placed his grocery bags down. Ignoring the second punch thrown by the villain, Saitama threw a punch in the man's direction. Before he even knew what was happening, the villain was hit by an intense wind pressure and sent flying back into a building. Sliding down the wall, he coughed out blood and slowly faded to dark.

Saitama reached for his bags, but he stopped when he saw a pair of shoes come into his vision. Looking up, he saw a slightly younger kid(?) staring at him with an intense gaze. Looking back at him, the boy did not say anything so he went ahead and grabbed the grocery bags. As he turned to leave, the boy finally spoke, "May I be your disciple?!" Pausing, Saitama looked back before shrugging.

"Sure," Saitama muttered before leaving for his house.

Later that night, Saitama would shoot up in his futon as he remembered exactly what happened. "Oh crap."

Woo! Saitama is officially in the My Hero Universe along with...Vaccine Man! Hehe...not just him, Marugori and...secret! But I think everyone knows who I'm talking about ^^

But yes, as mentioned, Saitama is indeed Quirkless in this fic, but that did not stop him from becoming as powerful as he is in OPM. Yes, I am focusing quite a lot on him, and that's because he is technically the main character of the fic, but I do plan on focusing more on Izuku since he's the 2nd main character of the fic. I just figured that you all would not want to see the same events play out as they did in canon.

To make things clear, Saitama is the same age as the main cast of MHA. I will decide on ages for any other OPM characters that I decide to add. Do not expect many characters to appear (besides throw away OPM monster villains, that are just people with monster-like Quirks).
Pairings...I'm honestly not sure, I am used to doing harems, but I'm not sure if I should do that.
So in the mean time
Saitama/?
Izuku/?

Give me your thoughts on the pairing situation. For now offer potential girls for either character to be paired with. And I will decide whether they will have harems or not by next chapter.