Exactly! Who else does he go home with and call stuff like *sshole, idiot etc (I don't think he can be that rude to a girl) . Also "What are people gonna think?" is more of a BL genre thing. I also would prefer to imagine that the black sleeve is in male's uniform.
I know it's supposed to be readerXcharacter but Kageyama is DEFINITELY speaking to Hinata. No one can convince me otherwise lol