Yandere! Younger Brother & Reader (Older Sister)

Highschool troubles and the hero

Other boys didn't like Saiyo, because of his frail body; to them he resembled a girl. They would gang up on him and push him to the ground.
You didn't like those people at all. You hated them so very much.
"Your so helpless", a group of boys came and tattered Saiyo into a corner.
He covered his face and cried endless tears, untill you came to save the day.
"Why don't you cry out to your mama?" They taunted over and over again.
"How about you cry, you jerk!"(Go reader-chan! Go!) You slammed your fist against the wall. An angry scrunched up facial expression shown.
"What? You gonna hit me, little pip-sqeak?" He squished your cheek, and you went in for the kill.
You used those beautiful white teeth of yours, and bit his hand. He staggered back in pain. You took your chance, and grabbed Saiyo's hand.
"You little--!" He stayed back.
You ran with his hand in yours through the hallways of your big school. You thought quietly to yourself, "I'm not always gonna be able to do these things."
You were right. You couldn't be a the savior of your own problems. That's why you have siblings.
~~~~Later~~~
You scouted around the courtyard of your school with loads of papers. The group of the, so called, "popular" girls strutted around you.
"Look what we have here, I guess spring really does attract horny bugs. "
You ignored her and sat on a bench near a pond. "Stupid girls" you thought to yourself.
"Oops!" A girl threw an empty case of makeup at you.
"Sorry my hands were full", she swung her red purse around.
You rolled your eyes and sorted through your papers. You had the urge to make a smart comment to them.
"Maybe it's heavy because of all the junk you keep in there."
They shifted their hips from side to side in annoyance.
"I think you mistaked my needs for your tacky style." They glared at you intensely.
Your fist was ready to launch. But before any physical contact could happen, Saiyo jumped in your way.
"Sorry for interrupting, but I'll need her for a sec!" He grabbed your hand and rushed away. You got to the other side of the building and panted heavily.
"Thanks for helping me back there" you smiled warily.
"That's what I'm here for, (Y/N)."
Siblings could almost sense when the other is danger. They just always seem to know where you are and what you feel. You were glad that you had each other, but would it always feel that way?
You shook your head violently. "No way!" You thought, shaking off your doubts.
"We'll have each other's back no matter what!"