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The battle had been a shit show up to this point, even Katsuki could admit that.
It wasn't a common occurrence after the fall of All For One but those big bads that gave them a challenge still surfaced from time to time. This particular specimen called themself Noyuu. The hasty analysis done by Izuku at the beginning of the battle had narrowed down their quirk as being reflective in nature, any hit or damage done to them they could store up and then release at any point.
Honestly their quirk reminded Katsuki a lot of Flect Turn, but this one was far more physical. It wasn't so say they weren't being injured but they were still able to dole out whatever was done unto them. It was a pain in the ass to deal with.
The stored up energy the bastard was holding on to also made them an unpredictable threat. This ability was seen in the way Katsuki got hit with a punch he was quite sure was leftover from one of Izuku's initial Detroit Smash hits.
He had been sparring with Izuku since they were teenagers. He knew what a full power hit felt like and it was a bitch. The fact that he was getting divvied out that kind of power from someone that wasn't his boyfriend only managed to piss him off.
Izuku caught him after a particularly hard hit, grunting from the effort of doing so. "Fuck, my bad. That was one of mine."
Katsuki spat out some blood that formed from where he had bit his cheek. "Not your fault, idiot. This bastard's quirk is presenting a legitimate challenge."
"It is. I think our only real hope is to outpace their ability to reflect our hits."
"Kinda like the shit you pulled in Otheon huh?"
Izuku gave a dark chuckle. "Something like that. It's similar in its basic essence but Flect Turn was a bigger nuisance than this Noyuu person is."
"Good luck tellin' them that. They seem pretty proud of themselves right now."
Their current aggressor indeed wore an arrogant smirk almost the entire time they had been fighting. It was like they were unbothered by all the damage they had accumulated over the course of the battle.
Which again, only pissed him off. Katsuki hated that shit because it made him feel like he wasn’t accomplishing anything.
”So what’s the plan, shithead?”
Izuku had a contemplative look on his face. “I’ll up my percentage of One For All and try to build up Fa Jin more, see if I can’t get faster. Speed must be the key here.”
”Kay, guess I’ll push out more explosions. The second rate cronies are all out right?”
”Yeah, I saw Red Riot drag them into custody at one point.”
And then there was one. Noyuu was going to be the hardest one to nail down, that was for damn sure.
”Then let’s get them too, nerd.”
Izuku flashed him a grin that was sharp at the edges. There was definitely some gremlin energy eking out into his person.
They moved as one, breaking off to approach Noyuu from opposite sides. The hope of it was that if they moved fast enough, the villain wouldn’t be able to dodge the both of them.
As they lunged, however, Noyuu pushed themself out of the danger zone.
Katsuki growled and slung out an arm to catch Izuku’s, then he used his own built up momentum to swing his boyfriend directly at Noyuu.
Which landed them a direct hit that the bastard wasn’t able to dodge. A nice big old kick to the face was the reward.
”HAH! YOU THOUGHT!” Katsuki couldn’t help but laugh.
Noyuu snarled in response and pulled back a fist to land a hit on Izuku.
His heart leapt into his throat for a moment, only calmed by the distinctive red glow around Izuku's body. Fa Jin was active.
Izuku moved out of the way at the last minute and landed yet another kick to their adversary.
Katsuki loved him so fucking much. It was a goddamn privilege to see that determined glow in those viridian eyes. To see the sharp light that would appear as Izuku honed all of his concentration into a certain move or quirk. To witness the way his boyfriend's lithe body would coil and flip through the air to land those crazy hits that only he could. He was beauty and power wrapped in one and Katsuki would never tire of watching him in his element.
The fight dragged on for a while more, getting harder as more and more time passed.
Their friends and colleagues worked around them, moving fast to secure all of the unsuspecting civilians that had been caught up in the initial attack. The amount of buildings that had been destabilized had been a staggering amount at first. Once rescue efforts had gotten under way, both Katsuki and Izuku had relaxed.
Now it was just a matter of bringing down Noyuu so that clean up could begin.
Katsuki was ready to go home. It had already been a long day spent on patrol. Following that kind of thing with an intense battle was exhausting for anyone.
"DYNAMIGHT!"
His head snapped up at Izuku's loud cry, trying to locate his boyfriend from where he had been maneuvering for an AP shot. The reason for his callout came in the form of a foot hitting him right in the sternum. The air in his lungs expelled itself as he let himself fall limp, going with the hit to minimize what damage he could.
It hurt, god it hurt. Not quite as bad as feeling his chest explode during the war, but bad enough to remind him of the incident.
He felt cool tendrils catch him - Blackwhip? - before he could hit the ground.
Izuku was there, pulling him away from the scene in an instant. "Fuck! Kacchan? How bad is it?"
"Mighta broke my strernum," he said through tight breaths. "Maybe a couple ribs. Damn. That was a good hit."
The tense hands holding him made it clear that his love was pissed. Izuku fell quiet as he got them to the ground.
"Mmm not gonna keel over, dumbass," he said through grit teeth. "Just gotta get the wind back in me."
"I'm not going to let this stand," Izuku growled. "This ends now."
Katsuki made himself focus at that. He peered up through furrowed brows to find an eerily calm expression on his boyfriend's face. "Izuku."
Izuku set him down on the ground and stood up straight. "Wait here. I'll be back."
It was only once he heard the distinctive clicks of a certain quirk being put into action that he realized what those words meant.
Oh, fuck.
Izuku was gone from his side faster than his mind could process, shooting up into the air after Noyuu at a speed he hadn't harnessed in years.
”Chargebolt, immediate backup required at the front,” Katsuki barked into the comms. Every too-fast movement Izuku made had his stomach swooping. This was going to be bad.
In their second and third years at UA, Izuku had only practiced using Gearshift three times. Each time he had requested Recovery Girl be present with both oxygen and an AED in case the blow back of the quirk was unmanageable. All three times he had needed the oxygen. Only once had his heart stopped.
So to have used it now, when neither of the emergency backups was in place, was a risky move. It was move that Katsuki could see leading to catastrophe if they didn’t act before the fallout hit him.
”Uhh roger, why though?”
The silence of the line told him others were curious as well.
”Deku used Gearshift. We might need you to reboot him.” The words felt heavy as he said them.
”He did WHAT?!” Cheeks screeched.
”Someone find a paramedic to have on standby for oxygen!” Was the callout from Red.
Katsuki couldn’t take his eyes off the fight. He was afraid that if he did, Izuku would drop.
”Chargebolt copies, on my way!” It sounded like he was running.
The impacts Izuku was landing on their foe were delayed, but not by a lot. Katsuki felt confident that his partner wasn't pushing himself into top gear or overdrive. The fact that the bastard had even lasted this long against Gearshift was remarkable. Further proof that their quirk wasn't one to be trifled with.
But he could tell that there was a shift occurring in the battle at hand. Izuku was moving faster than Noyuu could react. It was the anticipated weakness of the quirk that Izuku had been banking on. Katsuki should have known from the contemplative expression on his boyfriend's face at the time that the impending use of Gearshift was on the horizon.
As far as he knew, there was still a five minute grace period where Izuku could continue to function but would be severely winded and probably pass out until his body replenished some of the oxygen he lost using the quirk. Anything beyond that five minutes lead into dangerous territory. The likelihood that his heart would stop also doubled around the six and a half minute marker.
If there was one thing Katsuki had learned over the course of the years it was that Gearshift was not a quirk to be trifled with. Izuku had told him of how different it had become as it incubated within One For All, but seeing it in training had been a whole different experience. Katsuki had watched back the footage from the intense one on one battle Izuku had fought against Shigaraki and All For One - it was almost beyond imagination how powerful the quirk had become.
Now he could only watch as this insane quirk was unleashed for the first time since their days as UA students.
Shit, shit, shit.
Three minutes became four became five. Every few seconds that passed made him feel like he was going to throw up. Izuku's form became impossible to track all at once and Katsuki's heart sank. Either top gear or overdrive had just been activated.
Six minutes.
"Kaminari, STEP ON IT!" He called into his comm.
"ALMOST THERE!"
Noyuu was blasted into the ground with a tremendous Quadruple Smash, there was no further movement.
Katsuki shot to his feet, looking frantically for his boyfriend. "C'mon, c'mon," he begged.
Izuku materialized in front of him, a few clacking sounds signaling the end of Gearshift's intervention.
Already he could see the effects that amount of usage had had on him. Katsuki's heart ached in his chest.
Bright viridian eyes were wild and unfocused as he stumbled forward.
Izuku all but collapsed into his waiting arms. "Fuck, I gotcha."
"Ka-cch-" his boyfriend attempted to wheeze.
"Shhh, don't try and talk right now. Save what air you have, love."
Izuku writhed in his arms, scarred hands clutching at his chest.
It was such a horrible feeling to watch this happen knowing that he couldn't help. To just sit there and watch the love of his life suffocate in front of him. Katsuki grit his teeth and held on tight, keeping two fingers pressed against Izuku's pulsing jugular to monitor his heartrate. The frantic thrum was a comfort, even if it was quickly getting into the danger zone. At least his heart was beating.
"I'm here!" Kaminari shouted, sliding on his knees to them. He put a comforting hand on Izuku's arm as he offered him a weak smile. "I'm here, Mido. Okay? I'll help however I can."
Despite his desperate movements, something smoothened out on Izuku's face.
Katsuki really didn't want to evaluate what that meant for the next few minutes. "He needs fucking oxygen. Dammit!"
This was torture. But all they could do was keep an eye on him as Izuku's skin went pale, his lips taking a faint blue tinge.
"Fucking Gearshift," he cursed. "I know it was necessary, Izu, but I hate this. I'm gonna make Goggles include a goddamn oxygen tank on your suit, I swear to god."
Kaminari patted his arm in silent commiseration. "Does anyone nearby have a medic near them to bring on scene? Noyuu is down but Deku needs all the help he can get."
"Negative here, I've been looking but I don't see anyone," Uravity reported in.
"Neg here too," Red Riot said.
"Ingenium is bringing an ox tank," Eyebags reported. "Just keep him breathing until then."
A slight relief then. Katsuki would take any win that he could right about now.
Izuku was tapping a pattern onto his hand. Katsuki cursed.
"Nari, get ready," he ground out. "He's doing an SOS signal. I think his heart is gonna stop."
Kaminari was visibly nervous but nodded. There had been an unfortunate amount of times that he had been forced to apply a precision pulse of electricity to a person in order to restart their heart.
He had it down to a science now, but Katsuki knew he hated doing it.
Iida slid to a halt nearby, toting the aforementioned oxygen tank and mask. "I'm here!" He was quick to get the air flowing as he slid the mask over Izuku's face. "We've got you, Midoriya," he said in a calming tone.
He felt better having more people there. Katsuki would have been losing his mind if he were alone.
Especially when Izuku just... stopped. His limbs went still and his frantic breathing halted all at once.
There was a terrifying quiet that folded over him. Katsuki let Iida yank Izuku from his arms so that he could begin CPR. It felt like all of his first aid knowledge had left him. There was only the mental fog of terror left behind. His boyfriend was dying right in front of him and yet he could do nothing but sit there. How fucking useless was that?
"Kat, you with us?" Kaminari asked, shaking him. "He's gonna need you when we get him back, man. I know this is awful but we aren't letting him go."
He nodded, clutching tight to Izuku's hand.
Iida's brow was furrowed with concentration as he continued to apply CPR. He ripped the oxygen mask back off and put it a safe distance away. "Kaminari!"
Kaminari made him drop Izuku's hand as he delivered a single shock.
Katsuki's mouth felt painfully dry. "Wake up, wake up, wake up," he pleaded.
Iida jumped in to continued CPR.
"Another!"
Izuku's body spasmed with the jolt of electricity.
A few more pumps of his chest and suddenly he was coughing and sputtering.
Katsuki's breath left him in a rush. "Izuku!"
They rolled Izuku onto his side and waited until he stopped hacking to replace the oxygen mask.
"This is Ingenium, requesting immediate medical presence at the center. Deku has been resuscitated but will need to go to a hospital. I believe Dynamight is also injured."
"Copy, I'm bringing a whole damn ambulance with me," Cheeks radioed back.
Katsuki switched places with Kaminari, hovering over Izuku's face. "Gearshift is off the fucking menu for the rest of your life, d'you hear me?? Fuck, Izuku."
Izuku stared up at him with half lidded eyes.
There was a high chance his boyfriend wasn't processing any of his words but that wasn't going to stop him. He pressed a kiss to Izuku's forehead. Idiot.
"I am taking a vacation after this shit," Pikachu breathed. "Holy shit, Mido. That was too close."
"Thanks, both of you," Katsuki told their friends.
Class Prez patted his shoulder and reached down a hand to ruffle Izuku's hair. "With all due respect, let's never do that again."
"He's gonna give me grey hairs before we even get married," he grumbled. This was going to speed up the process too. Katsuki was going to put that ring on his idiot's finger as soon as he woke up at this point. He wasn't going to waste another moment.
"S'rry," Izuku whispered.
Katsuki laughed in pure disbelief. "You had fucking better be! But shut up for now, nerd. Just rest. I'm here. We're here."
"Mido, you are seriously built different. Sheesh."
"I am very glad to see you awake, Midoriya, but please rest."
The nerd passed out shortly after, breath hitched but steadier than it had been.
(Katsuki kind of wished he had been able to see Cheeks floating a whole EMS team and ambulance over her head though, that was wild.)
(Also the verbal scolding Noyuu got from everyone on scene for making Deku use Gearshift was legendary.)
(Izuku got scolded too, by everyone he knew, but he took it with a sheepish smile.)
(Katsuki loved him so damn much.)