Summary: Whenever Izuku is Emotional, his Quirk reacts by kicking him into high gear. Unfortunately (?) for Izuku, it happens half the time.

Note: Who even let me…

WARNINGS: Kinda Cracky In Places, Creative Usage of Feels, Quirk!Izuku, Self-Indulgent Quirk Rambling, Canon Events Slipped In-Between Izuku Mentally Rambling About His Quirk, No Really, Artistic License: Physics And Sound Waves, Jumps Around Canon Events.

Disclaimer: Don't own BNHA.

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Midoriya Izuku's Quirk was… unique, to say the least.

At first, people assumed it was a speed-enhancing Quirk.

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Four year-old Izuku tugged at his mother's skirt as he pointed at the hero figurines on display; his mother promised to buy him one of All Might and he was so excited, he was vibrating in place.

Inko smiled at her son as she walked over to the store's entrance.

Her son, in his excitement, ran up ahead of her.

Except, when he ran, he was a blur shooting with impressive speed forward. Impressive speed he had no control over, which caused him to stumble, trip and fall to the ground. Instead of crying, he shot up again and looked back at his mother with sheer enthusiasm.

"Did you see that?!" He shouted, "My Quirk! My Quirk!"

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But then Izuku discovered that his Quirk didn't just enhance his speed.

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Izuku stared at the bent wall among silence from his peers. He had just punched it in excitement over the new All Might movie, and it just… bent inwardly.

Everyone knew his Quirk made him fast and he was scrawny with no muscles to speak of; so how-?

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"Midoriya-san, it appears that your son's Quirk doesn't just enhance his speed but also his strength. You said he didn't hurt his hand, right?"

"Yes."

"That means his Quirk augments his body's speed, strength and sturdiness. But for a short amount of time, and it's always fueled by a burst of emotions."

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Midoriya Izuku, age: 6, Quirk: Emotional Rush.

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Izuku liked to analyze Quirks and his own was no exception. So far, he figured out that his Quirk increased his speed and strength, made him practically invincible while it was active, and it activated whenever he felt a particularly strong burst of emotions.

He felt quite strongly, which meant he unintentionally activated his Quirk a lot.

And that was how he figured out the drawback to his Quirk.

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Inko sighed fondly as she saw her son curled up on the floor, staring blankly at the wall.

"Izukkun, it's time for lunch."

Izuku made a sound at the back of his throat and rolled to his room.

Inko sighed again and pulled her son using her Quirk, lamenting how her son's Quirk left him drained after it activated.

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No one knew just how many functions of his body his Quirk enhanced aside from him. No one knew how wide the range of emotions that fueled his Quirk was, better than him.

And that was why, when the slime villain rushed at him from the sewers, when the terror roaring in his veins kick-started his Quirk, when he opened his mouth and screamed so loudly he probably would have seriously hurt his ears if his Quirk didn't prevent it, he wasn't surprised in the least.

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He was saved from the villain, and was left shaking in his shoes due to the aftereffects of his Quirk.

And then he saw All Might in the flesh.

The sheer, transcendent excitement of meeting his idol woke his Quirk again, causing it to metaphorically grab him from rock bottom to launch him into the freaking sun.

(He was, once more, reminded of why it was a Very Bad Idea to activate his Quirk multiple times in succession as he lied on the ground, empty, with All Might hovering over him worriedly.)

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One of the greatest challenges Izuku faced was gaining a measure of control over his Quirk so that he won't launch into a Rushed state (as he called it) every time he got overly excited and/or nervous. Which was basically 90% of the time.

As he stared at the U.A building on the day of the entrance exam, he was completely and intimately reminded of why it was such a challenge; he could barely take a step or, heck, breathe without his Quirk being on the verge of activating.

And that was a Very, Very Bad Idea.

He needed to save his energy for the practical exam and there was no way he was taking the written exam while simultaneously gathering every scrap of energy he could muster post-Rush.

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At least, Izuku thought, staring at the city construct and listening to Present Mic, the amount of emotions he kept at bay so far was bound to last him a decent amount of time-

"START!"

"WHOO!" Izuku shot like a bullet towards the city, leaving a small crater, a trail of dust and silent, gaping fellow examinees behind him.

"That's the spirit!" Present Mic shouted, "What are the rest of you waiting for?"

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One of the most embarrassing things about his Quirk was that it also fueled his ramblings.

"Ohmygod," He stared back at where the zero points robot stood awkwardly in place as its leg were bent where he kicked them, "We almost died aretheyforreal-?!" He continued on in hysterics. His fellow examinee whom he just saved, the nice girl with gravity manipulation Quirk, patted him on the back in an attempt to calm him down.

Izuku halted just as abruptly as he shot off at the start of the exam and toppled to the floor. The girl freaked out, "Hey, are you all right?! Are you hurt?"

"Nghhh." Izuku ignored her and curled up, god, he just wanted to sleep.

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It was highly embarrassing, "I'm so sorry for ignoring you back then!" Izuku rambled, "It's just, my Quirk leaves me tootiredandIkindofuseditmorethanusual-"

"It's okay!" Uraraka Ochako smiled at him.

"If you're all done." A man in a sleeping bag rolled into view.

Izuku stared in awe at him, was this man their homeroom teacher? Would he teach Izuku the arts of lethargic rolling in a sleeping bag? Izuku needed that particular skill in his life like nobody's business.

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A Quirk apprehension test?

Izuku fidgeted nervously; oh god, a test on the first day? Well, that was U.A for you. Izuku was enough of a nervous wreck to activate his Quirk on command- actually, he was barely holding his Quirk back, if he relented even for one second it would totally-

"The student who ranks last in terms of points will be expelled."

Izuku's Quirk high-fived him in the face with a fist.

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"Why does your hero costume have a skirt instead of pants, Deku-kun?"

How could Izuku tell Uraraka that it was to make sure that no matter how tired he got, the sheer embarrassment of wearing a skirt would be enough to fuel him?

(At least she didn't ask about the tiny writing on his sleeves; there was no way he was going to explain how helpful fanfiction was in fueling his Quirk.)

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Izuku looked at the villains in the water and gulped, "I… I can do it. I can jump there and get them."

"But they'll hurt you, Midoriya."

Izuku smiled weakly at Tsuyu, "My Quirk doesn't just enhance my speed and strength; while it's active, I'm practically invincible."

Izuku breathed in, out, before he let his fear and anxiety consume him.

His Rushed state engulfed him and he leapt into the air.

He sucked in as much air as he could, pushed the most of his Quirk towards his throat and shrieked at the water.

If he couldn't physically attack the villains, then he'd pull a Present Mic.

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Izuku didn't know what type of rotten luck he had to be told 'I'm going to beat you' by the strongest student in class.

It wasn't like he hadn't trained at all for the sports festival.

And so, he looked Todoroki in the eye and said, "I'm going for it with all my might, too."

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The first event was an obstacle race. It was the exact sort of set-up that put Izuku at a disadvantage, considering his Quirk.

There were other events after, and so, he had to be sure not to overexert himself at the first event in a way that would prevent him from reaching the next event.

Izuku breathed in deeply, eyes closed and mind focused on his Quirk. His Quirk activated in bursts with very good results; the speed, strength and durability he could reach with his Quirk going 100% in one go were astounding, from an objective standpoint. But it exhausted him, and doing multiple bursts in succession was digging himself a deeper grave.

If he could play around with the effects of his Quirk and their extent, then he could go from doing it at full throttle for a short amount of time and ending up being burned out, to doing it at half power, or lower, for a longer period of time, achieving a steadier input and slowly burning his energy so that the eventual tiredness won't be a shock to his system.

While the set-up put him at a disadvantage with what he was comfortably knowledgeable about of his Quirk, it was a good testing ground to experiment with his Quirk.

(Unfortunately, he didn't have the chance to leisurely experiment, all of it would be in the middle of an all-out challenge everyone and their mother were gunning to win.)

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When the race started, Izuku pushed forward, his Quirk rushing through him putting him at the head of the pack. With every step he took, he reduced the influence of the Quirk on his body, leaving him in a steady run with a small stream of energy enhancing him.

One of the upsides of not having his Quirk in full effect was keeping his mind clear and stopping himself from spontaneous split-second decisions. And so, he jumped, using the shoulders of the other students with him in the lead as steps instead of just jumping clear of them all (had his Quirk been running full power).

He rushed through the first obstacle in the course and went on to face the next.

He was aiming to tell the world that he had arrived, and for that, he'd need to use not just his Quirk, but every trick at his disposal.

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Izuku wanted nothing more than to flop to the floor and nap. Except he couldn't, not at the moment; he hadn't used his Quirk to its full extent through both the race and cavalry battle (even though he came close, during the latter).

And, more importantly, Todoroki wanted to talk to him alone.

Izuku braced himself.

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"Are you All Might's illegitimate son?"

Izuku choked, "What? Where did that come from?" Izuku was bewildered, was this about Izuku having a Quirk similar to All Might's? Sure, the most obvious physical enhancements done by Emotional Rush could be easily considered similar, but he was sure the technicalities were all different.

Then again, he never had a reason to explain his Quirk to his classmates in excruciating detail.

(And he thought it was just a one-time thing, bringing up the similarities.)

"Look, I know the effects may look the same, but I'm completely sure that All Might's Quirk is nowhere near the same as mine." Izuku flailed his arms around, "There is no way that All Might is related to me like that. I already have a father. Sure, he's rarely around and the last time I saw him was years ago and-"

"Midoriya."

Izuku snapped his mouth shut.

"If All Might is not related to you like that, then how is he connected to you? Everyone saw you two talk more than once outside of class."

Izuku sweated bullets, how could he explain that the first time he met All Might, his Quirk went haywire and he ended up distracting All Might as a result which caused All Might to run out of time while Izuku was rambling to him a mile a minute?

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Izuku inwardly cursed himself as a haze descended on his thoughts. He had one job! And he went and failed at it.

(And Ojirou had warned him about it, too.)

Now, where was he supposed to get something to hit him to get him from underneath the effects of the Quirk?

His frustration and anxiety welled up within him, rising higher and higher the closer he stepped to the outline of the ring.

His feelings reached the edge before his Quirk metaphorically threw him over it. His Rushed state coursed through his body, intense and hot and burning before it fizzled out in its usual fashion, making way for fatigue to slam into him like a speeding truck.

He reeled, falling on his back and gasping, he looked around him, noting that the only haze in his mind came from being tired instead of under the control of Shinsou's Quirk.

He breathed in deeply and refocused on his Quirk; he'd have to catch a nap later but he wasn't going to be as tired as usual, thankfully.

Pushing himself up, he rushed Shinsou.

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Izuku prepared himself to face off against Todoroki both mentally and physically; a fight against someone of Todoroki's caliber would require him to pull all the stops. He'd need his Quirk at max.

He did not expect accidentally meeting Endeavor before the fight would push him towards a Rushed state before the match even started.

For once, the feeling pushing him into Rushed state was anger. For once, his mind was clear during it.

Izuku giggled as he stared at Endeavor with gleaming eyes, "Oho? I don't know if you need your eyes and ears checked or something, but you clearly missed the memo: this match will be between me and Todoroki Shouto, not between me and you and definitely not between All Might and you. Better to quickly get rid of your habit of seeing Todoroki-kun as an extension of you, it's pissing me off."

Izuku pivoted on a heel and continued on to the arena.

(One of the things about Rushed state was that whichever emotion triggered it could influence Izuku's attitude during its activation period.

He wondered what being angry would mean to the confrontation between him and Todoroki.)

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The match started, and Izuku found himself facing an incoming ice glacier.

He took in a breath and screamed, the sound rattling the ice and cracking it. He took the opportunity to bulldoze his way though; the ice, already unstable and shaking, broke down under Izuku's frontal assault, completely incapable of grasping onto him.

Using his superior speed, he cleared the ice and reached Todoroki in mere seconds, and lashed out with his leg towards Todoroki's left side.

If Izuku was going at 100%, then by god he was going to make Todoroki do the same.

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The match was brutal.

Izuku did not relent and never left Todoroki a chance to breathe, consistently aiming for his left side in a bid to pull his flames out.

But at the same time, he made sure to pull his strikes enough not to seriously hurt him.

Izuku did not allow himself to strike the strongest he could manage without seriously harming Todoroki until Todoroki used his full Quirk.

And when that finally happened, when Izuku had screamed and struck hard enough to drag Todoroki's flames out into the open, Izuku allowed himself to kick Todoroki out of bounds before his Rushed state fizzled out and he toppled to the floor, completely exhausted and almost blacking out.

"Winner, Midoriya!"

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Izuku dragged himself to the arena to face off against Iida.

He was still exhausted, he had been running on fumes since some point halfway through his fight against Todoroki; there was no way he could put on half a decent challenge against Iida and they both knew it.

It was no wonder Iida won the match.

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Izuku knew himself well enough to tell anyone how strongly and quickly he feels. His Quirk just enabled it and helped him with it at the same time; he never had the chance to bottle emotions for a long period of time before he hit his threshold and his Quirk made itself known.

(Cathartic screaming into the void was one of his many past-times in his Rushed state.)

And so, when he heard about Iida's brother being attacked, Izuku was the last person surprised about how he tackled Iida into the ground, wrapped himself around him and refused to get up or let go until his Quirk's effects faded.

He was emotionally rambling as well; there were many a tearful 'mama will make everything better my child', 'hush my child, let mama take care of you', 'do you want blankets? Hot chocolate? Mama will bring you everything', 'my son my son I care about you very much, mama cares about you very much' and 'I need to fucking punch a wall or something'.

("Wait, is he calling himself 'mama'?!"

"He's declaring himself Iida's mama?"

"HE JUST SWORE. OH MY GOD, MIDORIYA JUST SAID –")

Thankfully, he was too tired to stay wrapped around Iida for longer than a few minutes, causing him to let go, dropping into sleep and setting Iida free.

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"Hero name, huh?"

Izuku stared blankly at his hands, wondering what hero name he could pick that would pass Midnight's scrutiny.

Pick Feels, a small voice inside of him whispered, giggling, and Izuku ruthlessly squashed it.

Izuku pondered for the entirety of the class period, and when it was his turn to show his pick of a hero name, he shyly walked up to the front of the classroom and showed his name.

"Swift Burst, huh."

Izuku nodded.

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Izuku stared at the decrepit building, hesitating before entering. Was this the right address? He couldn't believe that the pro hero who trained All Might lived here.

Oh well, he had to go and check at least.

As he opened the door he was greeted by the sight of a small, old man slumped over in a puddle of red.

Emotional Rush slammed into him, sending him shooting through the air to land next to the man (he dearly hoped he wasn't dead).

He was about to roll him over and see the extent of the injury when the old man snapped his head up and declared, "I'm alive!"

Izuku leaped back in surprise, slamming into the wall behind him and sliding down it to the ground while staring in shock that was quickly fading to give way to tiredness as he slipped from his Rushed state.

Oh, great. What a nice start he was at.

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Izuku stared at Gran Torino, then back at the taiyaki; what did he just say about distribution?

He'd always had his Quirk distributed equally in all of his body and it was only in the last year that he learned how to slightly skew the balance toward one part to strengthen it, which was how he rendered his unholy screech into an effective weapon.

He'd though about lowering the energy input to lower the chance of crashing after each Rushed state.

But what if he consciously pushed all of his Quirk's energy towards one aspect or one part of his boy?

That would require thorough testing.

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Izuku stared at the wall of the hospital room he, Iida and Todoroki were in before he sighed and turned to the other two.

Their faces were marked by fatigue, Izuku winced, "I'm really sorry. I had no idea my Quirk could affect others."

Todoroki looked at him, baffled, "That was your Quirk?!"

Izuku nodded.

"Midoriya," Iida started, "You never told us what your Quirk was other from it being a body enhancement Quirk."

"Well." Izuku chewed his lower lip, "It is, technically. But it's also more complicated than that? It's called Emotional Rush. At first, I thought it was a speed enhancement Quirk, but then-"

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End.

Emotional Rush is basically a collection of various feels in Quirk form.

This fic was pretty much an exploration fic, as it's my first BNHA fic that is not a crossover and covers events depicted in canon (unlike Flame Hero which is set pre-canon).