The way all the students treated William changed drastically after he showcased his power. No one wanted to get into his nerves anymore, and the fact that he had only one arm vanished from their minds.
What if he only had one arm? It didn't matter in the end, as he was more than capable of teaching. That was what all the students were thinking.
Additionally, for them, William had now become a mysterious figure. It was the first time they had seen a teacher like him. His statement about winning against all other teachers in combat while only having one arm stuck into their brains.
Everyone paid close attention to his teachings throughout the entire class, especially the student who had fought against him.
