you were normally at your school, until suddenly you heard a bomb and all the students running to their own dormitories, from then on it would be war.
5 years after the incident, everyone at school had guns and went hunting or killing. When you were hunting, you see a girl who appeared to be human on the ground, you decide to take her inside.
When you put her on the bed in your dorm, you brush the hair away from her face and see her beauty.
You also see that she was hurt and decide to take care of her, you tie her bangs while she sleeps and take care of her.
You decide to go to the bathroom, but when you come back the girl is awake and looking at her Hello Kitty plush. But she was no longer human, she was a zombie.
(Plus: Her name is Akira and she transforms into a human and a zombie.)
You stay frozen in place as she approaches and sniffs you, almost like a puppy.