Before reading this, I want to remind you English is NOT my born language, I'm a frenchie who TRY to write something cheezy in english. Hope you can enjoy that short fanfic with all the grammatical mistakes.
Okay class, hand to hand combat practice, no quirk involved, spar for 5 minutes after switch partner.
-YES AIZAWA SENSEI!
The 3A class where training under Aizawa supervision for a few minutes now and everything went well until a loud bang bein hear followed by a scream of someone obviously in pain and everyone froze in place. All eyes turn toward Kyoka Jiro who where screaming in pain with her right arm entierely bruised . Izuku run fast to the girl and catch her before she felt on the floor due to the pain.
-Ky..Jiro-chan! What happened.
-I don't fucking know, I was sparring with the little pervert, he was perving again on the girls, making me furious as usual, next thing I know I punch him and my arm hurt a lot...it hurt Izuku.
-Stay still, i'll bring you to recovery girl.
Izuku grab Jiro bridal style with extra care for her arm and start running at full speed to the nurse office.
-Eh...someone can explain me how Jiro just punch Mineta with what look like a strenght enancing quirk...and he is still alive?
Iida as a good class representative was next to Mineta and checking on him.
-Sensei can I bring him to getting medical attention?
-Yes go ahead, the rest of you go back to the dorm, class dismissed!
Recovery girl just finish treating Jiro's wound with a recovery kiss and was questionning the young lady what happened.
-I don't know, I just want to punch the little perver because he was peeping on the girls as usual and next thing I know it's like I use Midoriya's quirk.
-W...WHAT? Can you repeat that please K...Jiro?
-I don't know why man, my arm got thoses purples veins like when you use your quirk and I shattered my bones like you did in first year.
-Oh no, oh no it's not good!
-What is not good Izzy?
-Midoriya, do you think what I think sonny? How she would have get it? You didn't give her?
-N...No Recovery girl, I..i..i didn't give her!
-Giving me what dammit! Izuku?
-K..Ky..Kyoka...I...I think you got...i think I gave you my quirk.
-WHAT?
-Sonny, I need to goes to the other room to heal your classmate, during that time you call the tall blonde bouffon and you tell him to bring his skinny ass here asap.
Recovery Girl exit the room with a concern look on her face and goes to heal the young Mineta who's waiting in the other room. During that time Izuku was paniquing on the phone talking to someone while Jiro was faberglasted by what she just hear. When Izuku hang up the phone he sit next to Jiro.
-Izzy, talk to me please. She put her hand in his. I'm affaid, what's happening.
-I...I'm not sure Ky, i'm sorry, i'm so sorry, I didn't want that to happen!
-Zu, what's that story about you giving me your quirk, you can't just give people a quirk.
-I..I'll explain you everything soon, you trust me Kyoka?
-Yes Izuku, I trust you, you know that!
-Thanks Ky!
A few moment later the door open again and this time it's the former hero All Might with Recovery Girl who enter the room. The two close the door and All Might look at the two teenagers with no idea of the situation.
-Young Midoriya, what happened, did you hurt yourself in training with your quirk, it's been over a year and half that does not happened.
-It's not me All Might, it's Ky..I mean Jiro who broke her arm while throwing a punch.
-Oh it's unfortunate
-She was using One For All!
Yagi choked with the blood he cough when Izuku say that.
-WHAT?
-Somehow I don't know how I gave her the quirk. And no she didn't eat my hair.
-What the fuck Izuku, eating your hair? That's fucking gross dude, who would do that?
-Look Ky, I..i think I own you a explanation. What do you know about my quirk?
-It make you incredibly strong and fast, and you can shoot thoses black whip things and you fly.
-That's a part of my quirk, the name of my quirk is One For All, it's a stockpile quirk who can be passed down to another person and that person stockpile more power to make it stronger, sometime leaving a part of his own quirk inside and pass it to another, I am or I was the 9th holder of the quirk, and now you are the 10th.
-But, how?
-The quirk is passed if the holder of the quirk gave DNA to someone and that person consume the DNA.
-And how you know that All Might sensei?
-It is because young Jiro, it is I who gave young Midoriya his quirk.
-What the fuck? So that mean?
-Yes Kyoka, you now have All Might's quirk, and I will become quirkless...again.
-Fuck, Izuku, no! I..I don't want to steal your quirk or your dream of becoming a hero, you are so close, schoolyear is about to end in a few weeks.
-It...it will be okay Kyoka, you...you will became a awsome heroine with that quirk combined with your jack...
Tears can be seen from izuku's eyes and he try to turn his head, he don't want Kyoka to see him crying. All his dreams, all his hard work, all his sacrifices he made the past 3 years for...nothing.
-Can..can I give him back?
-I'm sorry Young Jiro, but the quirk can be passed down so someone only once in a lifetime, previous holder alerady try it in the past and it did not succed.
-Shit, I don't want that, i'm so sorry Izuku, I didn't want to steal your quirk!
-Don't be, you didn't steal it, somehow I gave it to you...oh shit!
-What happening young Midoriya, you know how you gave it to her?
Izuku became extremely red on his face and he start stuttering more and more.
-shitshitshitshitwhathavewedidyestedayshitshitshi!
-Izzy? Zu? IZUKU?
-I'm sorry Kyoka, it's because of yesterday.
-Yesterday? You mean when? Oh fuck! Seriously?
-It's the only way I can think how you have get my DNA in you...
-Can you two explain us what happen yesterday?
-Well..eh...you see...Kyoka and I are dating for a few months from now and...we didn't tell anyone cause we don't want any ructus in the class, you know how they can be in that class of morons and..
-And how that explain she can have eating your DNA young Midoriya?
-Well...heh...she...
-For fuck sake Izuku just say it dammit, I gave him a blowjob yesterday and I swalloed everything he gave me cause we where horny as fuck!
-...
-...
-...
-DAMN SON! I DIDN'T KNOW YOU HAD IT!
-NOT THE TIME ALL MIGHT!
-SORRY CHIYO!
-Well, this is a akward situation you two are now. What are you going to do?
-To be honest I have no idea, soon the remenant of the quirk will leave my body like it did to All might two years ago and I will become again a useless
-Don't finish that sentence Izuku, you hear me?
-But Kyoka!
-No but, we will find a way to reverse it or some shit like that, you will became a hero Izzy, understand?
-I don't know Kyoka...i...i need some time. He get out of the chair and start running out of the room.
-IZUKU!
Midoriya start running and he never stop, somes peoples shout his name but he ignore thems and just run out of the school. He never stop running even when he became out of breath and when he didn't have any strenght left in his body he just collapse on the ground in foetal position and cry. He didn't know how much time he stay here in that position crying his soul, shouting in his head how much life is not fair with him.
Few hours later Kyoka and All Might find him on the ground, he look like he passed out from exaustion or crying and they where concerned about him. The tall blonde man pick him up in his arm and carried him in Recovery Girl office to put him on a stretcher. Few moments later he regain consciousness and see his girlfriend sitted next to him holding his hand, Recovery Girl, All Might and Nezu speaking to each others in the other part of the room.
-Ky?
-Zu, you're okay?
-Yeah, I...i'm sorry for running away like I did, it's just
-Hey I understand, it's a pretty fucking shit that happen to you now, but we will find a way, it will work because I belive in you mophead.
While the two teenagers discuss the three adult have another talking.
-We need to try it to restore young Midoriya's quirk, it's a gamble but it can work, but if it work we will have to find a explanation of why young Jiro devlop that quirk.
-First thing first, we need to try it on Midoriya, the longest we wait, the less chance we got to help him, All Might, can you go and seek her help.
-Off course principal, i'll be back in a few minutes.
All Might exit the room and the two remaning adult come to talk with the two teenagers.
-Young man, we may have a solution to help you regaining your quirk at full capacity but we need to find a explanation for her.
-I think I may have something we can work on. You remember last week Ky when we work together during our internship, the villain we encounter together?
-Yeah, what she did to our quirk was pretty fucked up.
-Care to explain young man?
-You know I intern under Ryukyu to help me control my flying ability this last semester and Kyoka is interning under Edgeshot to help her with her stealth training, last week we have a joint mission with both heros and when they where busy with someone Ky and I where dealing with a vilain on our own. We learn after the fight that lady have a quirk who let her boost other's people quirk but during our fight she use a trigger dose and her quirk went haywire, I remember she hit us with a energy beam from her hand while I was trying to shield Ky from her, it completely messed up our own quirk for a few minutes, I remember I start running even faster than I ever did than I crash into a building.
-Yeah and I remember my earphone jack went crazy they stretch longer than I ever did and they get stuck in a car I was not able to get them out before Zu rip off the car's door. We where lucky Edgeshot saw what happened and he went from behind to knock her down.
-Maybe we can cook a story with that and tell people the trigger alterned her quirk effect and since you where toutching each other it transfer mister Midoriya quirk into miss Jiro.
-Yeah but people will ask why he don't have her quirk Nezu?
-We can pretend since Ky have a mutation quirk it work differently and I have...or had a emitter one only mine was passed to the other.
-This can be a good idea, we will stick to it, good thinking mister Midoriya.
A knock on the door have been hear and All Might enter the room with a 10 year old girl with white hair.
-ONICHAN! Eri run and jump in Izuku's arm and bury her head in his neck.
-I'm happy to see you Eri, you're okay?
-Yes, I was with Lunch Rush sensei and we where cooking apple pie when All Might came to ask me to follow him. Will you came taste the pies later, I bake them myself.
-Off course Eri-chan.
-I want to taste your pie too unicorn!
-Off course you can come too Neechan! I love when you and big brother Izuku spend time with me. But do you know why All Might ask me to come here?
-Young Eri it happened something bad to Izuku's body yesterday, he does not seem hurt but somehow he lost his quirk and we wonder if you can use yours to help im?
-Like I did to big brother Mirio last year?
-Yes deerie, do you think you can do it.
-Off course Grandma Chiyo, for big brother Izuku i'll do it.
-It's perfect sweetie, we need you to rewind him for around 2 days, can you do that?
-Yes, Papa learn me how to use my quirk and now I can rewind someone without hurting them or rewind them too far.
Everyone get out of the room exept for Izuku and Eri, she close her eyes and her horn start growing a little and a pink light glow from it. She touch Izuku with her hand for only a few secondes and after that her horn stop glowing and she retract herself. She open her eyes and smile at her favorite hero.
Izuku smile at the girl he consider his little sister and close his own eyes and try activate One For All, it work perfectly and he look inside himself and he can feel the quirk is still here like it never leave his body. For a few secondes he can see the shadow of the past users and he recognize Nana Shimura who where smiling at him, telling him everything is fine and they consider him still worthy to keep the quirk even with the mistake he did. He smile at her and awake from his little trance while desactivating his quirk.
-Thanks you a lot Eri, you really save me today.
-It's what heros do no? I learn that lesson from you big brother!
-And you will be a incredible heroine in the futur my beautifull Eri, thanks you so much.
-I love you Onichan!
-And I love you too Neechan!
Everyone return in the room and wait for the news.
-It's seems Eri quirk rewind my body just enough I didn't lose my memory of the past events but I manage to get my quirk back, I activate it and I can feel the quirk is here at full power. Thanks again Eri. Now Why don't you return to your cooking lesson with Lunch Rush, we need to talk adult's subject but I promess you Ky and I will come later to taste your pie.
-Okay, see you later big bro and big sis.
-Bye sweetie.
Eri leave the room to return to the school kitchen leaving the others to have a chat.
-So, what are we gonna do now?
-From now young man we will start a training regiment for miss Jiro to help her using her newly devlopped quirk during the month detention you both get.
-Detention, for what principal?
-You confess having sexual relation on school ground.
-Wait what? There is a no sex rule in the dorm? Since when?
The three adult look at each other before laughing leaving the two teenager with question mark on their face.
-We where joking, but I think Midnight will have to give a sex ed class to at least the 3th years students before we end up with a pregnancy in the dorm. For now you should return to your dorm, your friends are probably worried for you two since you where gone for a few hours, and we will set a training session for miss Jiro to help her with OFA. You do realise you create something incredible today you two, you literaly manage for One For All to be in two holder in same time at full strenght, nothing can impress anymore from you mister Midoriya, now go and we will meet again soon.
-Thanks you a lot principal Nezu, Recovery Girl and All Might, thanks you a lot for your help today.
-Yeah thanks and again sorry for..you know, all that crap we end up with.
-Does not worry Young Lady, this is the kind of situation we pro heros deal with every week, well not that one but sometime worst. I remember one time I save that kid who manage to turn a complete river into vinegar and I get it on my eyes and
-We understand All Might, we are leaving now, come Zu!
-Y..yes, thanks again you three!
Kyoka and Izuku drop by the kitchen to thanks again Eri and taste the delicious pie she bake before Aizawa arrived and bring her to their appartment, sending the two students back to the dorm before the curfew. Izuku and Kyoka enter the dorm holding hands and everyone look at thems when they enter the room
-You okay Jiro?
- What happened to you today?
-Did they find why you became as strong as Midoriya?
-Speaking of Midoriya, why you two holding hands, don't tell me you'r...HO MY GOD, YOU'RE DATING AND YOU DIDN'T TELL US, SINCE WHEN? HOW? WHO CONFESS?
-I told you Ashido will goes crazy when she hear about us.
-I know Zu.
The two teenagers spend the rest of the day explaning to the rest of the class what happened that day. Yes they are dating now, yes it's serious, for a few months, and no we didn't tell you guys cause we knew you'll all blow shit for nothing, no Mineta I will not tell you if we had sex yet or if her boobs are soft, no Ashido I will not tell you if I have saw his dick and yes he have a killer body. They explain with the fake story how Kyoka end up with Izuku's quirk and nobody know if it is permanent, so this is the reason they spend so many hours that day in the medical bay. Everybody buying the story and everyone offer to help Jiro because she need to learn how managing that new quirk she got, everyone remembering how Midoriya broke his bones everytime he use it in the first year of school. When curfew hour came everyone was leaving when they saw Izuku and Kyoka kissing, saying good night to each other. Mina called for a emergency girls meeting in Yaoyorozu's room grabbing Kyoka by the hand, knowing she will have to answer too many question about her not so secret anymore relationship with the class cinnamon roll. The guys leave Izuku alone knowing he won't speak under any torture they can inflict him, only Bakugo who know the truth about One For All want to talk with him a few minutes to learn what really happened, Izuku tell him everything happened only ommiting how she get the DNA inside her. After that Bakugo offer him to train her to became even better than Izuku ''just to see her kicking your fucking ass Deku''
Epilogue
Few years later the pro heroes duo of Deku and Hearphone Jack, the most powerfulls heroes in Japan with both of thems having a similar strenght enhancement quirk, where celebrating their wedding on a sunny summer day, both heroes smiling at their guests and waving at the media who where here for the world to witness the most beautifull day of the two symbols of peace, with the bride happily touching her perfectly round belly before the groom pick her in his arm and taking off in the sky of Japan for their honeymoon.