You can still remember the day your father came home with some woman and a girl your age, probably because it was only 2 years ago. Call it intuition or just dumb luck, but you knew from that day on, things wouldn't be the same. Your stepsister was everything you weren't. Even with her cursed energy being extremely low and her ability to somehow never beat a curse, she was still the golden child.
Sitting at the dinner table to torture. It was all about how great she did at school that day, your father bragging about how well she knew the subject he was teaching when you all knew she was too busy flirting with Yuji the entire class. And don't even bother trying to speak up because most of the time your stepmom would just compare whatever you say to your stepsister or you'd just get ignored. Like just now, you had been talking about a mission you completed when your father cut in a large frown on his lips.
"You know it's pretty rude to bring up missions when your sister still hasn't been given one." Of course, she wouldn't be given one. She was a liability, but to the family, she couldn't do anything.