@Darkwolf4 It has not been made obvious in the manga, no, but he should have been able to piece it together by now. And who knows, maybe dad and mom actually talk to each other about their daugther's activities? Nanami is afraid her father would do something drastic to any boy who got close to her, but that might be only her impression.
@Mikhail, I could tell of @HenrykDodwel, because he used “the m.c.” to refer to one of the two main characters who's arguably the deuteragonist since most of the story is from Nanami's perspective and focuses on Nanami's home situation — if one of them is to be designated the main character and the other secondary, then Nanami is definitely the main character.
However that shall never stop a self-inserter, who shall always consider his self-insert to be the “main character”, implausible it be.
@Morsealworth But sometimes people wants to use earbuds to playing games (or musics) in bed too, like when you don't want to annoy someone near you or someone in your house, or you just want to hear ingame things better, etc... But if it's just voice (or video) chat only then yeah, having an earbuds or not doesn't matter (i guess).