Eri was feeling a little sad and you and Aizawa noticed that and started to look sad yourself because EVERYONE HATES to see Eri sad and they would do anything just to see Eri smile, especially Aizawa, her caretaker

Deku:"...NO! NO! ERI SHALL NOT BE SAD!"

Kirishima also says that, Aizawa is worried but doesn't show it its sad at how broken Eri looks like sad