@Speak_Evil @Moribden
lol gave up way to easily. That is harsh considering a knife stab in the gut.
From the context, I feel that the sister isn't actually mad at the mc for running away but mad at herself for what the mc has become. Since it was shown the they are close, the sister probably blames herself for what happened and how he turned out.
The sister probably stayed away from the brother because she thinks it might happen again but as she grew older she tried to make it up to him. She might have tried to cheer him up but got rebuffed by the MC. Remember how he acts at the first chapter.
Remember, she has a successful career while the brother got rejected for 10 years applying for a job. He might have lashed out one day and strained the relationship.
If the sister doesn't care for the mc then she wouldn't have had that 'at least fight back a little' monologue. She wants the brother to buck up. It might be harsh but considering how he yells at his mom and holes up in his room buying stuff, hes not exactly gentle either.
Think about it, the sister has a good job but still stays with the family.