"Elder sister of the human king"? I would assume that she's the princess's aunt on her mother's side. Or does he mean sister-in-law? Or is the family tree more like a family dreamcatcher?
Considering this manga throws a lot of curveballs, I'm guessing auntie's strict attitude is just a foil and that she treats Suya in some way she finds annoying, which is why she's so reluctant to talk to her aunt
@JaffaOrange "Elder sister of the human king" mean she is the current king's big sister who is princess's father. So she is her aunt on the father side
@trieuvuhoang
I know I'm replying to a 6 month old comment but I still want to point out that both the princess' mother and aunt have stars in their eyes which is, at least according to the wiki because I don't recall this being stated prior to this chapter, a mark of the royal family. So unless they are somehow granted upon marrying into the family I think @JaffaOrange might be right about the "family dreamcatcher" thing