The reader's quirk is called Blood Lust. The Reader can eject and harden her own blood outside the body. The downfall is that her body must consume blood on a daily basis to compensate for the blood lost or else her quirk slowly starts to consume it's own body resulting in occasional 'blood lust' when the Reader loses control and does whatever means necessary to satisfy her blood lust. However, if the blood lust is fulfilled and extra blood is consumed she gains temporary enhanced physical abilities.

The thundering roar of the students filled the room with an unmistakable energy where the thrill made your blood pump like a raging rapid, boil like a furnace, fueling your ego. Wasn't before long that the class witnessed as their classmate threw her head back with a chilled gremlin howl and a crimson glint to her eyes. It was like watching beast marking their prey for dead.

Izuku Midoriya, he's known you since day one and yet not once in all of his days have he ever been as afraid of a classmate as he was at this very moment. Was it because he's all so aware you're out for blood? It didn't help that with every passing second the claw cannon gauntlets strapped to your arms and your fangs that practically glinted with a reflection in the light made the moment to follow all so much ever taunting. Will Midoriya die? Will he win? Will he even get out of this fight unscathed? At times Midoriya wished fights like these didn't count for a grade…

Vlad King and Shouta Aizawa stepped before the taped boundaries of the fighting  arena side by side. Although they taught two separate classrooms, their lessons were one in the same. Two hero classes, merge them together for one big assignment, fight. It’s an easy way for the teachers and classmates to learn first hand about combat by witnessing their classmates beat each other shitless cause why not?

Aizawa cleared his throat; he wanted to put a stop to your howling charade of blood lust. It was hard to believe that you’re the daughter of a respect pro most of the time… "Whoever makes it to ten points first wins," Aizawa sighed, sharing a bored glance with Vlad.

"You’ll gain points when you land a critical hit, knock your opponent out of bounds or you automatically win if your opponent cannot fight or surrender. Rendering them immobile doesn't count. You both understand?" Midoriya and yourself nodded together like a mirror image to Vlad’s half of the instructions. “Now… Play nice (Y/n). Don’t hurt him too badly.”

“It’s Midoriya, Daddy,” your smile stretched from ear to ear and he mimicked your features with relief.

“Have fun,” Vlad stepped away leaving Aizawa to do the honors.

“Should I take that as your word to… Not kill your classmate?” Of course your teacher had his doubts. Bakugou’s a grenade, explosive once the pin is pulled and can be dodged with ease. Not necessarily true, but he’s nothing compared to you, an atom bomb. Sometimes you’ll go off, and when you do, there’s no dodging it.

“We all know I won’t kill Midoriya now quit asking and let us fight,” while Midoriya was relieved to hear he’ll live to see another day, sing another song and save another life. Midoriya, speaking from experience,  was more than aware that was warning number one. Nobody should postpone your fights. If your blood lust isn’t fulfilled it means game over for everyone in more ways than one.

“Alright, don't kill each other," Aizawa shrugged. "Begin at any time."

Before we get into the fighting, here is the gauntlets your character will wear on both arms. I spent a good hour searching for what I had in mind and cropping the pic. The claws are just like Toga's syringes with the design of Grewishka's claws from Alita. The claws/gauntlets can be used like knives and shoot out at any given target as well as steal and eject blood from the victim or user to help fuel the Reader's fucked up blood lust of a quirk in battle.

"My pleasure!" You kicked out from your spot. The rubber beneath your boots squeaked loudly with the friction present.

Midoriya yelped, running away as fast as his feet could carry him with his quirk to aid. Anything that'll keep him as far away from you and your deadly claws as possible. Midoriya found himself occasionally glancing behind himself with you just feet behind. "Please tell me you were telling the truth (Y/n)! You aren't gonna kill me!? Cause you know I can't go all out on ya!!!" Midoriya began to plead.

"I promised!" You whined and slashed at Midoriya with your claws yet he was just out of reach. "I could never forgive myself if I did steal your life!" You swiped at him again, just barely grazing his costume to show off some skin. "Just keep in mind I have to satisfy my hunger!"

"Your definition of not killing me better not be cutting off one of my arms and calling it good!" Midoriya spun around with a high kick. It was his right leg, which meant his foot will collide with your left side.

You jutted off to the left with haste, ejecting your claws in which they successfully landed in his right calf. Midoriya bit his lip to suppress a scream. "As long as I'm satisfied you'll survive," you reassured Midoriya all to trigger the suction in your claws.

Midoriya nearly fainted watching his precious crimson become vacuumed into the pipes that connect himself to you. It was the astonishment that you had landed the attack that stalled him briefly. "I'm not just gonna stand here and let you do this," Midoriya snapped back into reality to grab the tubes all to rip the claws from his limbs. The boy of green hair jumped backwards like a rabbit for distance.

In response to this, your body switched gears from suction to ejection, chasing after Midoriya once again with claws drawn. "Can't run forever Bunny-Boy!" You cackled, the crimson you harvested from your victim shot out from your claws like a laser. Mentally you commanded the blood to harden upon contact, tripping Midoriya up by his ankle alone. That didn't hold Mr. Bunny Ears himself for long, a simple jerk of his leg and the crystalized crimson shattered into glass!

"Quit running!" You hissed, ejecting more than just the harvest blood from your claws to drench your victim head to toe in crimson. Your arm went pale by the time he was evenly coated and hardened with the inability to escape.

"You could've just let me get my fill," you wobbled on over to Midoriya's crimson cocoon, even using it to keep balanced and upright. "I was only gonna… Gonna take enough blood that you passed out and our fight would be… Be over…"

"(Y/n), no," Midoriya couldn't move, doesn't mean his lips can't. "You could've told me that earlier. And you need to sit! You're so pale! You're probably about to go into shock!!!" Just how much of your own blood did you use to trap him here? Enough that your lust hasn't kicked in and you're remaining sane. That means you've either had your fill of blood, which clearly isn't the case, or you're about to pass out.

All assumptions came into the light once you fell flat on your back, rewarding Midoriya as the victor in the fight.

-----

You came to roughly… Six hours later. Even then you could barely see only to realize you're lying in an uncomfortable wire bed of white. The nurse's office. Everything felt heavy, limbs refused to move. As badly as you'd like to know what the painful stinging sensation was in the middle of your right arm, you couldn't move enough to see exactly what it was. Either way, it was as if a knife were penetrating your limb.

"Thank goodness you're awake!" Someone took a breath of relief. It was Midoriya for sure, you couldn't mistaken his high pitched voice of worry for anyone else.

"I… don't know why I'm in this shitty bed…" You groaned.

"We fought in class," Midoriya fiddled with his hands. "You used too much of your blood on me and passed out. By the way, your dad dropped by and he says he's proud that you didn't kill me."

"Oh," you pucker your lips. "Well… I'll be out of… You know what, speaking from experience I won't be fighting anyone for the next month and blood transfusions will be my best friend until then," cause that 'stinging' in your arm must be the needle that delivered blood from a clear bag to your veins. "Say Bunny?"

"Y-yes (Y/n?" Midoriya cocked his head at first, that's the second time you've ever called him Bunny. Nevertheless he stood up from his chair and got closer to you.

"Even though I more than likely stole some of your blood, you were my donor again weren't you?"

Midoriya stalled, he had to create some sort of response. "I didn't want to say goodbye to you yet…"

"Too much blood loss and you could've died too!"

"You needed to be saved and I'm a hero!" Midoriya did a double take. "I-I also love you, and love makes me do stupid things…"

Of course he'd say something like that. "You do realize you're dating a sadistic girl who drinks blood on a daily basis right?" It didn't stop him from nodding his head. "Sometimes I wonder what you see in me that keeps you coming right back like a glaive… Those things kill, and you kill me with kindness."

Somehow, Midoriya figured you'd argue and make a reference to something deadly. "Whenever your quirk isn't doing all the talking, you're sweet. Is that enough for you?" You opened your mouth to disagree. "Yeah, don't bother. I know I have to say more," your boyfriend read your mind, and so you waited for more to come. "I mean it though, you're really scary like Kacchan most of the time, but whenever your lust is quelled you're the most fun and loving girl I can ask for. Just like how I love that nickname you gave me!"

"Bunny?" You hummed.

"It's cute! Just like my new name for you."

"And that is?"

Midoriya jumped into the air, "Does Bat sound fine? Like Bat and Bunny crime fighting duo!" You could faintly see Midoriya punch at the air, grab and arrange his hair to make ears, as well as fangs with his index fingers.

"I like it," you snickered. "Killer Bat and Cuddly Bunny."

"Now can you quit questioning why I love you?"

"Yes because I'm tired and wanna sleep again…"

The end of this x Reader was a nod to the anime Tiger and Bunny. It's like MHA except there's adults instead of kids. Highly recommend you watch!