"I need my brother… he takes care of me. My brother has never hit me before, not even when I was really bad. My brother. Brother. My. Brother. Brooother. Brother. Brother."
The worry that filled Byleth's face instantly caused her chest to seize with worry.
However that happens to someone's chest is beyond Mercedes, but that expression the professor had cause her chest to have a seizure. Not only that, but why was everyone worried?