The girl who has PTSD

After she lost her oldest sister from a car crash and her mom from giving birth to her little sister, Mimiku has a terrible disorder that she's just fighting for her life which is PTSD so everytime she hears loud noises or her little sister, Nora, screaming to remind her mom and her oldest sister, her mind breaks letting her insanity out on innocence including her dad because all she's willing to do is protect her little sister the same way her oldest sister protected her. Now that Mimiku has transfered to a new high school, she's away from Nora for a long time until she graduated, luckily for her she made some friends named Kimchi, Jade, Linda, Cecilia, and Carol. Little did they know, is that Mimiku has a inner self if she hears something that relates to her older sister's or her mom's death and Mimiku is trying her best to not show it but told them not to make any loud noise until something bad happens to them. Will she tell them why she's telling them not to make loud noise? Is her inner self gonna get to them first before she can?