Uncontrollable Hatred. [Yandere! Katsuki Bakugou X Reader]

( Prologue )

Three twelve year-olds sat against the swings belonging to the local park. On your right; Izuku Midoriya, while on your left, sat to be Katsuki Bakugou. Every day, you all would converse and venture without a care in the world... However, today was special. You undergoed a proposal from a boy with dark green hair, and bright eyes. His small freckled face was always lovable, it made it only cuter to see a soft blush remain against them.

And about the proposal? It was a promise.

Midoriya leaned away from your ear, and within a second; a brief nod had left you out of understanding.

"Okay, uncover your ears, Katsuki." You pulled against his hands to bring them down, feeling as he submissively followed your movements. "Why couldn't I listen to Deku's promise...? I wanna know about it, too."

Frantically, Midoriya shook his head, his eyes widening. "No!! It's between us! I'll.. tell you later..."

Bakugou looked at you, who seemed calm. Your smile remained, enjoying the company of your two best friends in the whole wide world. Honestly, you three were inseparable, and didn't know how to let go.

During your moment of isolation, Midoriya would have quickly looked into your direction in an instant.
"S-So.. do you promise?"

You crossed your arms as you began to ponder, keenly digging through your undeveloped mind as you tried to come to a firm decision. Finally, you opened one eye, staring directly towards him with almost a smug smile. "I'll only promise you once you've finally develop a quirk." You afterwards snickered, causing Midoriya to furrow his eyebrows and for his lips to purse. "Wh.. What?!"

He knew it was impossible, but yet he still had hope within him. The glisten in his green hues danced with inspiration, and he stared at you with an almost puppy-eyed look. "Do you swear, [Y/N]?!"

You nodded your head, pushing yourself against the swings a bit while your tiny hands clenched the chains. "I swear." Although you thought that was enough to satisfy him, he didn't back off just yet. He'd lean into your direction. "Swear to All Might??!"

"She-Sheesh! I swear to All Might!!"

The next thing you knew; the boy with green hair stood right in front of you, preventing you from swinging too freely. He grasped onto one of your hands which was previously wrapped around the chains belonging to the swingset, this movement earned your glance. His fingers folded down, all except for one; his pinky finger.

Midoriya wrapped his finger around your own and shook it gently, his cheeks in a bare red. "Don't forget it!"

Upon hearing your silly conversation, Bakugou had sighed abruptly. "[Y/N], Deku won't get a quirk as better as mine, don't get his hopes up. We all know that he won't get a quirk at this rate." A cocky cackle left Bakugou, leading you to hit the back of his head roughly.

You, on the other hand; had a quirk that allowed you to minimize, and maximize only objects by your discretion. Your quirk proved to be very convenient. Give the item a quick touch while keeping the ideal size you'd like it to be in mind, and there you have it! Extremely simplistic it ought to be.

Midoriya narrowed his eyes and then pursed his lips, meanwhile you and Bakugou had begun to playfully attack each other. You both had your grasps on each of your cheeks, pinching and pulling them without any remorse.

"Leavf... hmp... alone!!"
(Leave him alone)

You protested, earning envious growls from the other. And as Midoriya snapped from his despondency, his previous irritation and sadness was now contorted into a look of frightful dismay, troubled by the sight of his friends arguing with one another. "[Y/N], Kacchan... stop it, please..!"

As soon as you heard his voice, you released Bakugou in an instant, and in return he had let go of you. "Sorry, Izuku! Are you mad at me? Upset?" Midoriya flinched by your abrupt change in persona. You had always had a soft spot for him, and you cared for him deeply. Almost like a little brother.

Bakugou brought his eyes away.

Why didn't you care about him like you did with Midoriya? He just didn't understand. However, since he had only been twelve years old, he didn't fully get an understanding grasp around the emotion jealously.

"Izuku isn't answering me.. he.. must be upset... I-I'm sorry!! I won't pull on Katsuki's cheeks again..!"

"N-No! [Y/N]! I was just surprised! If you cry... then it'll be my fault.."

Bakugou had always been an energetic child, but whenever he saw you smiling, being sad, angry.. all at someone else... it tore him apart. It made him feel an incredible amount of emptiness he never thought was possible.

Especially when those emotions you shed weren't directed towards him, but towards Midoriya.

He eagerly yearned for your attention. Don't get it wrong-- you loved the both of them and treated him like you were the best of friends, which you were, however your feuds often got in the way of things. Though it was safe to say that Bakugou was simply... misunderstanding.

Your gaze lifted up and at the setting sun over the beautiful horizon. The view guided you to a quick realization. Midoriya had stopped patting your back after you shot from the swing set. "Right! I need to help grandma!! I'll see you two tomorrow. Sorry for pulling on your cheeks, Katsuki, and sorry for making you worried, Izuku..." A sloppy, apologetic bow left you. Bakugou approached you, just as Midoriya began to.

The boy with red eyes reached to pat your head, as this was typically his own way of saying his temporary goodbye. "Whatever, just get home safe. Let's play together tomorrow!"

They sought you off briefly with small waves. But as soon as you had finally departed from their eyes, the boy with green hair would clench onto his yellow All Might T-shirt, right where his heart belonged. His gaze had fixated onto the ground with a cherishable smile, while his green eyes sparkled in a warm gleam.

Midoriya's flustered demeanor caused Bakugou to glance over. He was now in a state of wonder, and something about this situation made him fall quiet, and for his heart to pace faster.

"Kacchan..."

"On [Y/N]'s sixteenth birthday, she and I.. will become lovers..."

[Prologue END]