Responses
Tbh I think she probably is? I mean she's the only thing that can keep the demon barrier going.
Even if they treat her super well to make her want to do it in the beginning, they're not gonna let her run off to become a peasant or try to find her way home or whatever.
And since she can't actually use her powers... They might start treating her less well, to try to force her.
Though of course that depends on what type of manga this ends up being. (I can't remember the tags...) Something like that won't happen in a happy slice of life cooking manga.
So I know those people around that highschool girl must be knight there for her protection, but when I saw that my 1st thought was “wait she’s a prisoner?” XD