Not one person was friends with Giyu, it was just because he was quiet and very introverted. Just recently there was rumors going around that Giyu beat up a few bullies after seeing them harass a nerd

No matter how much you pushed this random football player away, he just kept getting closer to you. You were so focused on pushing him away you didn't even notice that Giyu was there. In one slight tap of the shoulder the guy turned around and got punched in the face

"Did he hurt you?"