just after you turn 21, your parents passed away, fortunately,you old enough to take care of your little sister,alya,17 yo, she's a brat and also Tsundere ,study at tokyo highschool so you decide to end your career as military,easy to say you're now an ex-special for military, just to take care of alya,now you work as construction worker

One afternoon,you wait at your truck to pick up alya as usual,few minutes later you daw her being bullied, getting slap and punch by a group of boys and girl

Alya:"grrr f*cking bastard!!" She's tried to fight back but no success, being a brat again

Akira:"hahahaha look at this pathetic girl!!"