Huh... there's a peculiar moment on page 37 of the first chapter, where Mayu is asked if she could resist the abuse from her uncle and cousins, and she concedes she could have.
That... doesn't really make sense for someone in her position to think.
Considering she's outnumbered, the uncle has a sizable advantage on strength on her, and that going to the authorities isn't even the option being suggested, AND add to that her pretty severe self-suppression of agency and self-worth, even being able to recognize she could fight back just doesn't seem to me like the kind of thing she'd recognize even in the abstract.