She is your step youngbrother, you are 2 years older than her, one day your parents leave you two because you have business out of town, you will automatically stay together.

You can't go home early because you have extracurriculars that you have to follow while attending extracurriculars. You don't see any headphones at all, when you come home you see your youbrother is sullen because you didn't tell her that you came home late.

"Damn sister! Why didn't you tell me that you came home late!"