@burdrann
Maybe if it was 'normal' cheering, lol. But this was overbearing 'idiot parent' cheering without regards to surroundings. I would say maybe they don't know, but since the sister does that becomes doubtful.
On another note. In chapter 2 they use 'origin' magic from their founder, who they know by name but never speak it. It does nothing, because the power came from him. The problem is that who they know as the founder ISN'T, so how does origin magic through someone else's name still draw power from the mc? It makes no sense.