When did it say that they have a sister?? I thought that was their mom?? (⊙…⊙ )
Same me too at first but then I saw michan(mc bro) calling her nii-san !
Nii- san means sister in Japanese
No, I don't think so. I remember he didn't have a sister bc he would talk about the common older sister plot and that he desired to have one. So I'm sure it's his mom, prob just a family nickname, like how some couples with children will call each other dad and mom (even though they are married).
Prolly she meant your brother ig? Sometimes a mom call brother for their older children
Was that his sister? So unexpected she's the real npc one here i wanna get to know her now, u know what npc with no face and names are much more interesting and mysterious here