Katsuki Bakugou x little sister (OC)

New brother?

"Class! After this maths lesson  get ready to go to ground gamma." Aizawa stated  his tired voice interrupted the kids.

" ohoho can I come pweaaaassssseeeeee!" Masumi pleaded with puppy dog eyes to the older Bakugou.

"NO It's TO DANGEROUS!" Katsuki screamed at Masumi.

"B-but whhhhyyyy..." Masumi whined louder.

"I ALREADY TOLD YA DIM-WIT, ITS DANGEROUS!" Katsuki yelled bending down to her level angrily in her face.

"Hmph! FINE! you just don't want me to come, I'll get myself ANOTHER brother if you don't want me." Masumi argued nose almost touching Katsuki's and a defiant look placed on her face.

After a few seconds of staring intensely each other Masumi blinked and trotted away.

"Tch! Whatever." Katsuki muttered.

"Kiri?" 

"Huh?" Kirishima felt a  pull on his trousers as he looked down to see a wide eyed Sumi staring up at him pleadingly.

"Sup Baby Bakugou class is about to start so make it snappy." Kirishima said flashing his famous shark smile and putting the child on his lap.

"You need to be my brother now!" Masumi stated bluntly.

"What? What do you mean?" Kirishima asked unsurely.  

"Weewwlll you seeeee i told nii-cha..I mean Katsu dat  he'sh not my brother anymore and, and i need SOMEONE  to be my brother!" Sumi Dramatically exclaimed to Kirishima as if it was the most important thing in the world.

"And...I guess you want... me to be your......new brother?" Kirishima almost chocked laughing.

"This is serious! Don't laugh!" The child pouted whilst Kirishima puffed out his cheeks to hold in his laughs.

"Oh-ok  and you sure your brother or ex-brother won't kill us both."

"Humph if he tries my mama will deal with him first and I'm pretty strong too!" Masumi said making tiny explosions dance on her fingertips.

"I guess it wouldn't be manly if I turn you down now would it!" Kirishima held out his fist for her to fist bump.

"YES MANLY..WWOWOWOW!" Masumi fist bumped Kirishima but was then lifted into the sky by someone she couldn't see.

"Huh?"she turned around to se a very tired and bored Aizawa staring straight at her.

"Oh hi Mr Catapillar!" Masumi gave him a cheeky smile and boped his nose.

Aizawa  rolled his eyes "if your going to be in my classroom you have to behave, you can't distract everybody." 

"Eye-eye captain!" Masumi saluted Aizawa as he carried the child on his back, piggy back style.

"So class if you remember correctly we use y=Mx+c for straight line graphs, using this formulae can you calculate the equation for this line." Aizawa said pointing to the board, "Urmm You come up and solve it." 

Mina came up to the board and solved the equation.

"Very good that..." Aizawa was interrupted 

"Actually it was WRONG!" Masumi yelled from Aizawa's back pointing disgustedly at the board.

"What!" Mina said surprised.

"Well." Sumi hopped of Aizawa, grabbed a random chair, pushed it towards the board, got a piece of chalk and stood on the chair.